Hi & welcome,
I would recommend choosing an army you like. Both SW and IG are very good army's that you can't really go wrong with.
Once you decide what army first thing you should do is buy the codex. Don't start buying the mods first. If you do that u won't wast money and time on ineffective squads.
I also recommend swatting up in the tactic section, it's where I started and there is a lot of good info there. Will improve your game no ends.
Write a army list and post it up on here. Ppl will be able to help you out. Prob best starting with 1 HQ and 2 troops first, about 750 pts. That is a good start and will give you a good point to expand from.
Gl any questions PM me. Here to help.