For simplicitys sake lets start with the primary Civ members
Warlocks
These are the most important members of the Civ, You'll only ever have a handful unless, like me you resort to shamless save scumming.
There are 3 times when you get warlocks 1. the embark 2. your first migrant wave 3. your third and final migrant wave.
Outside of buying skills during embark warlocks are restricted to Research, Writing, Alchemy and Chemistry, Herbalism, Medical Experiments, Working with Gems, Trading and sorcery
they can use magic and are required workers for many high level workshops
Ghouls
These guys are crucial in the begining. Warlocks NEED bodies and souls basically right from the begging 2 or three ghouls set as a military squad and ordered to attack local wildlife can supply that need -they're fast and somewhat durable. In my opinion their importance fades over time as the skeletons become more important but in the beginning ghouls are key.
To help with this role their natural butchers - they'll hunt down Kea's rip the heads off and after you.
order them to dump the bodies next to the butcher shop they'll rip out the meat/bones/souls for processing
They're created at the Graveyard - there's supposed to be a way to create ghouls from caged prisoners but In my experience it just creates loyalty cascades - Graveyards the way to go.
(also if later in the game you want to armor them stick to leather, they need to stay fast to hunt down wildlife metal Armour slows em down)
Skeletons
Its likely you'll end up with some skeletons in your embark typically I made them miners or stonecrafters to carve out a shelter/ provide hourglasses.
But their real role is in the later game - they dont sleep - dont tantrum -dont eat or drink - they can fight - and they can do most non-magical crafting.
They don't learn skills normally and must be deliberately trained at the inscriptor.
Vampires
Vampires are tricky - I never got the to work you're supposed to be able to keep them inline with blood wine - To keep a steady supply of blood there's a special pet (Bloodpig or something -no wait a blood goat) that can be milked to provide blood, but in my fort Milking resulted in a blood filled bucket which I couldn't figure out how to get it into a barrel, which is important because to make blood wine you need a BARREL full of blood rather Than a BUCKET. My inability to supply bloodwine meant that every vampire alive in my fort posed a threat to my precious warlocks as feeding is fatal.
hence forth all vampires are starved to death in a locked room.
The Actual Embark
Embarking on top of a necromancer tower provides a level of defense as all warlock units are UNDEAD friendly. you'll want as many warlocks as possible all though its RNG based so if you only get 1 out of 7 as warlocks the only out is to abort the fort. You also want atleast one ghoul whom you should buy a few skill levels with dodging, and biting.
you'll also need miners and wood cutters (usually skeletons).
But you also need crafters, a mason/carpenter a Stonecarver now usually warlocks cant learn this stuff but by purchasing the skills at embark it becomes doable
unlike dwarves you probably need 2 anvils, rather than one
Starting off build a crafterswork shop a carpenters and maybe a masons you want doors beds and hourglasses
send your miners off to carve you out a shelter. and the sick your ghoul squad after the local wild life. Build a soul siphon near you're other buildings asap and make some stone hourglasses at the crafters workshop(rotten corpses provide no souls , and souls rot rapidly - these next steps have to be done quickly ) .
Once your ghouls have successfully killed a couple badgers or whatever have the build you a butcher shop and then designate a dumping zone near by.
using dump commands have the ghouls bring the corpses back to the butchershop, reclaim the bodies and make sure butchery is enabled on your ghouls.
the shop will be spitting out souls/meat/bones in no time - Make sure sorcery is enabled on your warlocks, then go to your Soul Syphon and order your warlocks to store
the souls in a phylactery - This stores the souls in an hourglass to stop them from rotting.
Make a totem out of some meerkat's skull throw in a couple stone blocks and 3 phylacterys and you can build a Necromantic Shrine(don't bother with necromantic circles they're cheaper but can only make uncontrollable zombies) this will allow you to start producing skeletons A warlock worker is required, alongside 8 bones a totem a scrap of leather I think and a single soul phylactery.
making a bunch of these creates you're workforce - but be aware if skeletons are away from warlocks for 2 weeks they turn neutral and wander around aimlessly - in late game you'll likely endup pasturing pylons(LARGE GEM and a Soul phylactery at your necro shrine) around your base to keep control over them - but in the beginning its to expensive- if a skele wanders off on you just create a military squad under overlord assign a warlock and station a warlock near by any lost skeletons, after a couple seconds your warlock will smack you skeletons around abit and they'll come to their senses (This is combat logged as "The Necromancer Takes control over an undead servant")
Once you have a good work force and a small soul Stockpile you'll want to build an ethereal gate, This is technically a Furnace so your hotkey s will be [b)[e][a].
It costs 3 souls and a couple stone blocks, it allows any sorcerer you have to make you furniture and blocks for free.
Later on you can create an ethereal forge which creates weapons and armour for free aswell but the melt after 1-3 months unlike ethereal gate products.
to make lasting metals you'll want a crematorium and a corrupted forge both under the [b)[e] menu.
The Crematorium can create ash from vermin remains/wood/bone aswell as coke(furnace fuel) from wood.
Add some coke and some ash to your growing bone supply from your ghouls wildlife expeditions and you have all you need to create some Iron bone at you're corrupted forge.
this is a cheap metal but I think its better than bronze - making a couple whips/ scourges for you're ghouls might be a good idea
also Making a graveyard to produce more ghouls might be a good Idea, as they make up your main defense early on other than walling yourself off(which really hurts you since you need to be collecting souls/ meat/bones).
Just be careful the job to try to create a ghoul has a 5% success rate(I think) and takes a whole stack of meat - irrespective of the number of meats
(so if you have 3 stacks of [Chipmunk meat(33)] you can consume 100 units of meat for three 5% success rate ghoul summoning attempts) add in the fact that ghouls only eat meat and unlike skeletons will tantrum without it means you have to be careful
What else would you like to know, all of it?