That’s a tricky one. Depends on what you’re looking to work on. It’s just like any other tools, you’re going to need site pushers for one, that goofy punch for assembling an AR…The list goes on. Ideally you need something with some brass punches and a hammer…
Vice blocks for A.R. 15 upper are nice to have. Super cheap…That some strips of leather, cardboard and clear boxing tape so you don’t f*** up your finish if that’s something you care about…
There’s also a ton of information on YouTube about how to do things with the wrong tools if that something you’re into. It’s not like you’re working on a registered m16 receiver or something when you’re done with it just throw it in the safe and buy another
Buy yourself some brass rod and cut it down into punches, get yourself a brass hammer you get a lot done with that.