First of all, do NOT concentrate exclusively on pick-up and seduction. It will fuck you up when you have a bad night if you don't have anything else going on in your life.
Start by improving your life. It's summer time. There's lot to do. Go to the beach with friends, go to the gym to work out and get in a better shape, do something productive, to make you feel better about yourself.
About the clothes a stylist could definitely help. That's what they are for. Even if most of them are gay, they know their stuff.
Mindset. Well yeah only from this post I can see how you need to work on that. The game is a learning procedure. When you study for something, you need to leave time for other things, or it fucks you up. The same goes with pick-up.
Trial and error pretty much speaks for itself. Just do your things and see how it goes, and make the conclusions. Try to guess where it went wrong.
Body language. There certainly are good books about this, but I think the easiest way to improve it, is by getting in a good state. Then observe your own body language when you feel that "nothing can stop me" feeling. And next time you don't feel it, try to remember your body language and mimic it.
Inner game. Well I pretty much covered that. You need self respect and an interesting life for a good inner game.
Good luck!
CHAT