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 !