First and foremost, I LOVE this mod, it's fascinating and fun, however, I struggled a bit with some things and some information is not so readily available, so I wanted to make a little guide with answers for those who want them.

How to get started
So, in your inventory there *should* be a book, it allows you to choose your difficulty and offers a few hints, for this guide we're gonna assume you chose the hardest difficulty because you hate fun and the world has crimson because you want it to be *somewhat* easier later.

Getting NPCS:
Mine the starting block until you get enough rain clouds to make a storm cloud, don't use it yet though, expand the platform and try to find pinky so you can make a slimy cloud, it starts the slime rain event, kill every slime until king slime shows up and get the solidifer from it, make npc houses out of slime (gross) and place them all in hell.

Getting Dirt/Mud:
Buy the anvil from the merchant and make an EoC Summoning item at the solidifier for 20 lenses, kill EoC and hold onto those corrupt seeds for now, if you're lucky you'll get 2 seeds, if you're not lucky fight it again, once dryad moves in you can buy ash grass seeds (Assuming she lives in hell.) and start planting grass on your ash blocks, then acorns, harvest the trees and make a leaky barrel and shovel (Anvil in a graveyard biome), fight some zombies with the shovel for dirt, stand near the leaky barrel for mud.

Building the Jungle Biome:
Use the corrupt seeds you got from EoC on *mud* then purify it using purification powder, or craft jungle seeds using the same 2 items, you should now have a single jungle grass block, expand it using whatever method you like, dirt bomb duping or zombie farming.

Building the [Evil] Biome:
This one is kinda obvious, but use the seeds from EoC to build a corrupt/crimson biome, for skyblock crimson is simply better, Brain of Cthulu isn't as movement restricted as Eater of worlds, so it's easier to deal with, you can't fight it yet, so be patient.

Getting an Altar:
You need to do the torch god event, place 106ish torches and dodge the resulting fireballs in the underground or lower levels, once you get the torch gods favor, place a few torches in hell to get demon torches (which you'd otherwise need obsidian for) so you can make an altar with [Evil] mob drops (Vertebrae/Chunks) and [Evil] wood (shadewood/ebonwood)

Getting Stone:
This one was a bit confusing at first, you should have a furnace from moving the merchant into the jungle biome, fight slimes until you get enough iron/lead to make a heavy workbench, put it in a graveyard biome and make cracked dirt, make it unsafe at a demon altar and place it close to the underground, but still on the surface, we need gnomes to spawn, they're relatively rare spawns and you need them to follow you into sunlight in order to become petrified, smash them with a crimson/demonite hammer and you'll get a shattered gnome, use it and it'll spawn a rock golem, kill that and viola, stone, repeat as necessary.

Getting Gems:
Using the stone you got in the previous step, grow some grass, harvest some blueberries and dye the stone blue, thereby turning it into granite, place it down in the underground and stand on it so granite mobs spawn, they drop more granite and geodes, crack the geodes open and look for rubies, using the dryad you can get more stone/gems via gem corn trees.

Getting Lava/Water:
Make a fire resistant bug net and go catch lava critters, your net will melt into a puddle of lava at some point, make sure you have a basin/pit to collect the lava in and viola, lava, dupe it enough to make a pond and go lava fishing, you'll get water bombs among other useful things.

Getting Sand/Snow:
Sand can be made at an extractor which you can fish up in a crate, snow comes from turning snow cloud (mine the starting block) into a snow globe and summoning frost legion.

Getting Honey/Dungeon Blocks:
Dropping a hive into water spawns a hive block, break it and there's a 1/3(?) chance you get a pool of honey, once you have enough hive blocks fight queen bee for wax and use the wax (among other things) to build dungeon bricks and unsafe walls via the Altar.

At this point there's not much variation between this and regular skyblock and the remaining hints are pretty straightforward except for a few I'm still working on, you should have a jungle, water, lava and enough information thanks to an in game recipe browser or wiki scroll to get to moonlord, maybe I'll update this guide if people have questions about specific things.

I'm not going to include a full guide for each difficulty because at a certain point it becomes redundant, and there are other biomes (I.E Desert/Snow) that can be made/used for progression, this is just the bare minimum to progress in case people get stuck.

Edit: I'm not good with formatting.