Cryts Guide

The first World Ascension is a huge step for any account, but knowing what comes after is a bit more obscure. By the time you are planning for a World Ascension you've most likely forgotten what you needed to get each of the important Town buildings to rank up, or what is needed to prepare for attempting Accomplishments for the extra World Ascension Points and Milestones. So, while not comprehensive (and most of this information will be present on other pages in the future), here is nearly all of it (or at least will be, since this list is still a work in progress) in one place.

First, What Not To Do

It is generally not a good idea to try to push Catalysts very far in the first World Ascension, as all progress of them will be lost after this, and the second Milestone removes this penalty, so its better to save the resources (as they wont be lost) rather than lose the levels, and instead work to cap your catalysts after you can no longer lose levels on them. A general recommendation for level caps of each catalyst would be:

Slime: As high as you want, as the only exception, its fairly easy to get Slime Oil, since you spend a lot of time grinding in slime areas for Auto Rebirthing, so this is the only one you'll always have a surplus of resources for. Because of the high level it also makes it significantly easier to farm Slime Balls, and you can never really have too many, as they say.
Mana: Between 10 to 20 levels. You will need a lot of Mana seeds to both unlock things pre and re-unlock them post World Ascension. So even though its a bit more costly, it isn't a bad idea to put a bit more of your time into this catalyst, as you will save much more in how quickly you will get the Mana Seeds you need
Fire, Ice, and Wind Catalysts: Level 5ish max, these catalysts are different, to be honest, the lower you can keep them, the more you'll save in the long run. They each need their respective shards, and Flame Shards are the worst offender for collecting. Other things, such as titles also use these shards, and they take longer to farm than Slime Oil or Magic Cloth, luckily you never end up needing more than 10 or 20 of any one of them (Unless you are preparing for some crazy first World Ascension shenanigans, in which case you wouldn't need this guide anyway)

Item Preparation

First to explain why equipment is important in the first place. When you complete a World Ascension, all equipment without an enchantment or open enchantment slot are destroyed. Normally enchantments are fairly rare for any given equipment to drop with, however the Thief's Equipment Mastery for every item is to instead give all versions of that item an enchantment slot, so the Thief can allow you to selectively choose what you want to bring post Ascension.

Long Swords, Long Staff or Dual Dagger - The only real thing to consider in the choice for these is which class you want to try to push to Rebirth the fastest for the World Ascension Accomplishments, in order of Warrior, Wizard, and then Thief. It mostly falls to preference, though quite a few people do go Warrior, as it has a decent balance of Tankiness to Damage. You want to have enough for each equipment slot (minus 1 for each class that has completed Florzporb's Solo Challenge, due to losing the bonus on World Ascension) for each class. This does include having Long Swords on your Wizard for instance, because the global levels granted by the item will help your chosen main class push further. You can very quickly get to Guild Level 15 to get the global skill slot, and then put whichever attack you would need to help the class that is suffering for not having the correct attack bonus type to continue progress.
One other Equipment type to take is Tower Shields (The Physical Variant). They have a fairly low drop rate, so holding onto a few (no more than your main class has armor equipment slots) has some value for something may not have pushed for before the first World Ascension: Zones past the Fairies. In order to increase the rank of the Cartographer Town building to 3, to let you reach the Level Milestone to unlock Foxes and... what exists past that, you will need to clear Bat Dungeon 2. The 2nd dungeon is actually rather difficult to survive, due to it being rather high level, and bats applying a Defense Debuff. All Bats do Physical Damage in Dungeon 2, and Tower Shields not only give Defense, but also give Physical Absorption, which greatly reduces the damage you take, making it significantly easier to clear the dungeon. The main reason to prepare this item is almost solely due to its low drop rate, as grabbing a few just before World Ascension is much easier then trying to grind them out when all of your stats have reset afterward. (Unconfirmed) If you could complete Bat Dungeon 2 before you complete your World Ascension, then the credit for completion should carry over, which would allow you to skip saving Tower Shields (Unless you wanted to save them to be able to run the Dungeon anyway, as it does have very high EXP returns).
Elixir of Brawns/Brains (based on which class you will push for Accomplishment Progress) - While your equipment is lost on World Ascension, your potions are not. A good way to prepare for the push through the harder dungeons at the beginning of the game is to level whichever matches your class to as high as you reasonably can (Both to reduce the chance it will be consumed when you kill a monster, as well as to increase its effect). At a decent level you can more than double your primary damage type, which helps significantly when dealing with both dungeons you are timing out in, as well as the Challenge Bosses. Since their consumption is random at the end of the day, a good amount is probably around 2 stacks, or roughly 30-40 of them, though it is possible to do it on 20ish, its just more comfortable with more.
Similarly to above, the Chilled Regen Poultice is rather valuable to have. With it at a decent level, you are nearly invincible in most of the early dungeons, and it makes face tanking Florzporb not entirely unreasonable. It alone can be a really good tool to stop dying in Dungeons you otherwise would have completed. Just remember that it is only consumed when you start an area, so entering a dungeon and then equipping the poultice, and then removing it just before you clear the dungeon, means you'll never consume one. Due to this, if you can remember to manage them, you shouldn't need more than maybe an single stack full.
Cool Head Ointment (WIP) applies an EXP gain buff while equipped, its strength and value are apparent just by its effect alone. Definitely one to bring a few stacks or even more of through to the World Ascension, as that extra EXP can help boost the rewards from a Dungeon and get you leveling faster than ever.

One extra step that can save a lot of time and pain is preparing the Catalyst Materials needed for Ranking buildings back up as you unlock them post World Ascension. This can get pretty expensive, so instead I will divide these into 3 Tiers, with each one implying you get every rank from the previous tier as well, but the shown total being the total needed to get all ranks (So don't add up the costs of each tier).

For Statue Rank 2, Alchemist's Hut Rank 2, Temple Rank 1, Blacksmith Rank 1, and Slime Bank Rank 1, you need a total of 300 Slime Balls and 50 Mana Seeds
Adding Statue Rank 3 and Temple Rank 2, you need a total of 600 Slime Balls, 350 Mana Seeds, and 10 Unmelting Ice
Finally, for a further stretch in preparation (Though I don't know this is strictly needed), Adding Blacksmith Rank 2 and Slime Bank Rank 2, you need a total of 1600 Slime Balls, 350 Mana Seeds, and 10 Unmelting Ice. As you tend to spend a lot of time running the Essence of Slime in lab, you will typically end up with more than enough for the extra 1000 Slime Balls needed, but in the event you don't have them for whatever reason, don't feel pressured to push that far.

Progression Milestones

The simplest recommendation here is to at least unlock the first rank of every pet up to the color Red and through to Fairies (With Red Fairy probably being the only exception), this can be rather time consuming, as Red Nets are easiest to obtain via the Capturing 100 Yellow Fairies, but every pet of each type gives something rather valuable, so it is worth it to do a sweep before World Ascension, as it gets a lot harder after the fact.

Expeditions are easily your lifeblood post World Ascension, as Town Materials are the biggest grind you will encounter. As such you should push to grind Expeditions as much as you can to help bolster their returns. While there are other benefits to raising expedition levels (such as other types of expeditions), the true value shines in helping you collect large amounts of Town Materials. The 3 things that effect this are:

Team Rank - The rank of the monster, only increase-able by either capturing more of said monster, or by sending said monster on the Expedition granting capture points
Expedition Levels - Just levels like anything else, not a whole lot to explain since you get these just by doing Expeditions.
Time - This one is deceptive, as while it will increase the amount of resources gained, it doesn't do so at the same ratio that it increases the time needed to complete. Meaning doubling the time to complete does not double the resources you gain, it appears to be closer to about a 70% to 80% increase.

Given that, and the fact that monsters return the same resources that you can get from their areas, getting as many Slimes and Magic Slimes to as high a Capture Rank and Level as you can is the most efficient way to boost expedition returns, and thus make the early part of post World Ascension significantly faster. I would also recommend generally focusing on the Manufacturing Bricks and Logging Trees Expeditions, as those two resources are needed significantly more than shards at the beginning of a World Ascension.

The highest tier of Rebirth you can get for each of your unlocked classes. Since there is a title quest for each, that increases their efficiency when in the background, getting that buff as high as possible is one of the best ways to prepare. That said it isn't strictly necessary to push all classes to the 3rd tier of Rebirth if it would take more time than you feel like spending, but all classes should have finished their 1st Rebirth at a minimum. It is also generally recommended that your main class has finished its 3rd Rebirth at least, since that is the class you want to progress the most, the fastest. Know that you only have to do this once, so if you really don't want to deal with post the 3rd tier Rebirth, you can instead plan to rebirth and complete the title just before you complete the World Ascension.

Raising the Alchemist Hut to level 25 for the +50 to the Purification Level Cap, as well as maxing Purification. The the levels of the Lab upgrades aren't lost on World Ascension, even if you don't technically meet the requirement to have that level cap, meaning while you would have to re-level the Alchemist Hut to level 25 if you didn't do it before the World Ascension, if you do complete it early, then you don't even have to rank up the Alchemist Hut at all to keep the benefit. Note that if you intend to complete Road to Alchemy 5 (see below), you will either need to increase your Mysterious Water Cap by taking Alchemist Hut's Leaf Research to level 10, or by taking the hut itself to level 40.

The Apprentice of Potion Title on as many classes as you can, though at least your main class and whichever class you intend to use to push for Accomplishments post World Ascension. The Apprentice of Potion Title gives you more Utility slots, allowing you to equip more potions and talismans. Each additional potion or talisman you can equip can potentially skyrocket your progress through the push for Accomplishments. By either letting you keep the IEH1 Talismans equipped while using the Elixir of Brawns at the same time, or giving you the chance to equip the Chilled Poultice of Regeneration to keep yourself alive. Even just one slot gives a large amount of flexibility to pushing dungeons and challenges in the early stages, even post Accomplishments as well.

Pushing The Road to Alchemy quest line as far as is reasonable. Each time you complete these quests, you gain bonuses to your Lab that are permanent and will significantly boost recovering your lost progress to your catalysts after the World Ascension. The most notable one is Road to Alchemy 5, which rewards a 25% reduced cost for leveling up catalysts. This applies both to its main item cost (Oil of Slime, Frost Shard, etc.) and to the Magic Water needed to level up the catalyst as well. By the time you unlock it you may not need it before the World Ascension, but because you will need to make at least one more push to level up catalysts after you ascend, it is easier and faster to do it when you already have a built lab, than when you lose all that speed.

Apprentice Equipment Titles, specifically the ones gained from Apprentice of Weapon/Armor/Jewelry. Obviously these are incredibly strong, but you should make sure to have completed at bare minimum 2 of each of them for whichever class you will push for Accomplishments with, and of course your main as well. All progress on these are lost when you complete the World Ascension (Though this is also true for a given class when it preforms a Tier 3 Rebirth, though you don't get to keep the equipment proficiency multiplier when you ascend), and each slot you get can give you a massive power boost in the available equipment you have. Weapon is objectively the most important, but the other 2 are easier to complete than Weapon, so it should be fairly reasonable to have all 3 at Rank 3 of the title.

Researches from the different Town Buildings also carry through World Ascension (though the building levels and ranks do reset, without specific Accomplishment Milestones from World Ascension). Of the researches there are a few that stand out specifically as being either incredibly valuable in general, or can help alleviate other early game pains post World Ascension. Remember that these researches and their suggested levels are just the end goal, and the order that you get them and when you get others not listed here is decided by you, the first three are in order of value, but after that are just honorable mentions and not an all inclusive list of which are good.

Temple's Leaf Research is easily the most important one in the game at the moment. Leveling it up is less a question of what level to stop at, and more a matter of am I OK spending X hours for one more level (The answer is usually yes). At minimum I would push as close to level 20 on this research as you can as this will always speed up one of the slowest parts of the game. I would only push past 20 if you are going for a particularly long first World Ascension, due to the Arcane Researcher building and its researches boosting your research gain rate, as well as how many things you can research at once, thus bringing the levels after 20 back down to somewhat manageable times.
Cartographer's Leaf Research is amazingly useful, as post World Ascension Town Materials become the largest gate to getting back to where you were before. While Expeditions can give a lot of resources, they are limited to only one type per slot per 30 minutes (at best), and so you will still need to grind out some of the other town materials, or just more of the one you are running Expeditions for. Its not surprising that the tutorial questline has you raise this research specifically. This should be the 2nd highest level Research you have, only behind Temple's Leaf Research, but at bare minimum I'd say level 10 is enough to stop at.
Statue of Heroes Crystal Research is only more valuable than the Stone Research, because it effectively does what that research does and more. This research helps you recover Resource Gain upgrade levels, as well as every other upgrade as well. An easy highlight is being able to get more equipment slots early, but the Research can also help push for the next tier of the Very Resourceful Milestone if you are close enough to it.
Statue of Heroes Stone Research is can just be treated as a way to help boost how quickly you can increase the maximum rank of your skills and gold cap. Getting it to 10 isn't a bad idea, but leaving it around 7 is fine too. I cant say pushing this one so incredibly hard has the most value, as the Resource Gain upgrades you can get from gold cap increase is probably more efficient to your time.
Statue of Heroes Leaf Research is a secondary help to what Cartographer's Leaf Research and what Expeditions are trying to cover. Initially this research is really to help you recover levels, but in the long run it will also help you push to higher levels once you get the further Accomplishments Rewards that let you maintain building levels.
Trapper Crystal Research doesn't actually need to be that high to be useful. It basically amounts to how quickly you can get traps, which of course leads to how many Capture Ranks you can get, as well as bonuses, stopping between 5 to 7 is fine, more is just if you like traps.
Temple Stone Research does what it says, but a bit more effectively the you might think. There is only one of each type of buff in the game, the only difference between an EXP buff you get from a dungeon chest blessing or the one you get from a swarm clear is the duration, but they all scale effect from this research. For just that alone it is strong, and it may even be able to help you edge over certain difficulty thresholds you might be limited in due to dungeon difficulty, but I cant say its strong enough to be something you dump all your time into. 4 or 5 levels is where I would leave this one for now, as each level only ends up being about a 4% EXP boost from the blessing
Blacksmith Stone research is extra base Auto-Disassemble slots, it is really a convenience pick, but not bad to help keep your inventory from filling up with equips you don't need. The Crystal Research is a bit deceptive in value, as this is one of the only ways to directly effect how quickly you progress for the World Ascension Milestone Pro Disassembler. Though it isn't strictly needed, as getting the first level is fairly easy for your first World Ascension.
Slime Bank Stone and Leaf researches are the two to focus on, but as you aren't likely to get the building to a very high level, the research level will cap pretty quickly. The Stone research is currently the only other way to get Slime Coins other than over-capping gold, and as it is passive, it can be very strong for long term returns, though its value increases as your cap and total held coins increase. The Leaf research's value is actually more advantageous for having the Slime Coin Cap upgrade lower than it would otherwise need to be to get the other upgrades.
Mystic Arena strictly speaking isn't really worth unlocking before your first World Ascension, but should you end up doing so, only the Stone and Leaf researches have any real value this early (as the Crystal research needs you to get further than you realistically will pre World Ascension to get any value out of, and thus will have a similarly long wait to get any value post World Ascension). The Equip slots from Stone research are self explanatory, and the Alchemy Point Gain from the Leaf research can make it significantly easier to level up potions and the lab upgrades. As this leaf research is one of the only ways to increase Alchemy Point Gain, it is a valuable stat, but not something worth pushing hard for this early.
Alchemist Hut leaf research at level 10 is required if you want to complete Road to Alchemy 5 (for the discount on catalyst upgrades) without taking the Alchemist Hut to level 40.

Quest Mastery is a slightly hidden mechanic, where you only really learn about it if you hover over the medal on any quest's description. What you are aiming for here should be fairly obvious though, even just completing the quest 100 times gives a massive exp boost to the quest, as such it can be really valuable to push for 1000 quest completions for some of the easiest quests. But that sounds horrid without a bit more context. There exists a quest line with the same name as its title reward, Quester. Which has the advantage of increasing the Mastery count an additional time per level of the Title, meaning just the first level halves the number of completions needed, and you can grind out more as you go. But there is also another reason to grind these completions out now, as of the current version (although I don't actually know if this is intended to change or not) when you preform a World Ascension, you lose your current progress on reaching the next quest milestone. While the quest will maintain any milestones you unlocked, you are treated as if you haven't completed the quest before after ascension, so it can also be worth it to push for the next milestone if you aren't too far from it.

Really Conditional

From personal experience, I can generally recommend these as more of a safety net, but may not strictly have been needed in the first place. Some of these are based on difficulties I had when I ascended and wasn't anywhere near as prepared as this guide will have you. But at the same time, better safe than sorry.

At least 10 (or 30 if you want to be really really safe) clears in Slime Dungeons 2 and 3 (Maybe MagicSlime Dungeons 1, 2 and 3 as well, but I'm not yet familiar with how the EXP re-balance has effected those dungeons). The main mechanic unlocked post World Ascension is Area and Dungeon Prestige, this recommendation is based on... well dungeon prestige. One issue I ran into was not having enough time to complete Slime Dungeon 2 due to not having enough damage just after ascending. An upgrade available for Dungeon Prestige is to increase the time you have in a dungeon by 60 seconds. While you can also achieve this through Cartographer's Stone Research, they do stack as well, and can be valuable with further prestiging (Not a word, but OK) the dungeon later on in your ascension. Plus you always have the option of just not spending the point on that upgrade if you end up not needing it, so no real loss if you over prepare there.

Before You Click Ascend

At this point you have everything above prepared to the point that you are ready to Ascend, like now, maybe 5 minutes maybe the next hour, maybe before you finish this sentence, but wait there is more! A few more things in fact.

Change your active pets. When you ascend you go back down to the limit of 5 pets, and which ones you have equipped will be left to Hitan's baby herself if you don't drop down to 5 beforehand. So an easy prep is to have them ready now. Generally the best ones to have selected are Normal Slime and Magicslime, as well as Red Magicslime. Past those 3, the last 2 are just what you find more convenient, though Blue and Red Slime are probably going to be the most common 2 picks.
Favorite Quests, a minor optimization, but presetting them can help you progress as fast as you can. Unfortunately all your extra quest slots are lost, so you are limited to 2 (or more if you spent real money). As such the easiest 2 to recommend are Slime Infestation 1 and Find My Brother 4. The point of this is to push for as much exp as possible before you can no longer gain any accomplishments, so outside the first one or 2 rebirths after you ascend, I'd probably only focus on doing those two and whichever quest matches the highest you can complete between Slime Dungeon 2 and 3.
Do yourself a favor, export your save. With the exception of this next step, what happens after here isn't within the purview of this guide, but instead one that definitely needs to be separate, however one thing easy way to save yourself so much pain is making a checkpoint here. If your grind for Accomplishments goes poorly, or more likely you just didn't understand your priorities this time around. It helps and save scumming this can save you boat loads of time in the future.
On a similar note remember that you can always export another save after ascension as a checkpoint as well. While you can always just load back to the original save if you think the new checkpoint was actually bad, it still does its job. Grinding for the Sub 1 hour Tier 1 Rebirth and Sub 1 hour Guild Level 20 to 25 at the same time can be hard, especially if you don't actually know if its reasonable for you reach Guild Level 25 for instance, so instead of making an entire 1 hour slog, run a couple of test runs to see just how quickly you can get the first Tier 1 Rebirth down, then once you are content with that time, export a save. After that just work from that save to try to get as many Guild Levels as you can. Much easier than trying an hour long marathon when you barely know what you are doing.
And finally the actual last thing to do, after you've made an exported save, but before you ascend, is wait. Yep you have to wait, on whichever class you will be pushing for Accomplishments with, but not for just anything, instead for a complete-able swarm. Any active EXP Blessing you have will be carried through World Ascension, so having a good 30 minute or more (With Temple's Crystal Research) is a nice way to get the ball rolling. It means a failed ascension leads to another wait before you can try again, and also a reason why that an export when the buff drops isn't the worst idea.

And with that you are ready. Well ready for what you do before you preform your first World Ascension, not necessarily with what comes immediately after. But after you hit that ascend button you are scumming for Accomplishments and their respective extra World Ascension Points and Rewards. I'm also not covering when to ascend in this guide, or at least not yet (If I even do decide to), I might append that section just above this paragraph in the future, but for now the only two tips I'll give for that is: "Don't Ascend at 5 points, get at least 6", and "More points is better".