Hey all!
Is there someone here that’s experienced with mini painting, specifically the priming part? I got some questions about it.
I recently got myself into WH40k tabletop - the whole thing. I got a painting set and formed a tiny army of 3 small squads that need painting. However, I just realized that I should also apparently prime them before real painting.
I suck at painting, but yes, you should prime them. Use white or grey. If you use a black primer and want light colors, you’ll be in trouble.
Prime them to get richer colors and to get the paint to stick better. I personally prefer black and never hadan issue with lighter colors but it depends on the quality of your paints i guess. Tldr always prime your minis. Most importantly let the primer dry properly before you do anything else
You dont really need a spray - the normal colors will workjust fine for the start. More work, but less mess - especially if yo have never sprayed anyting 
Always use a primer.
White primer is harder to master, as you’ll have to retouch many colors again if you don’t do it properly.
Black primer offers a natural shade, but colors look darker on it.
Check out ‘siren games’ shop. They have a good selection of paints and other modeling tools, including minis.
Citadel spray-on primer works well with citadel products (technically it’s not a primer, but bonds well with their plastic). Army painter spray on primers also work fine and are cheaper.
For metal minis, and oder plastic minis like reaper bones, i would definitely recommed vallejo acrylic brush on primer. It is awesome. For example black brush-on primer, followed by gray/white zenital spray-on primer 
If you really bite into the hobby consider investing in a spray gun, makes priming and painting much easier and more fun.
You can find all this stuff at that shop i mentioned.
Definitely prime your minis. It makes painting more fun and richer, and saves money on buying paints.
Also, if you haven’t, check our on internet how to make a wet palette.
Welcome to the hobby i sretno !