Make a new account, dick around on it. Play off meta picks, weird builds, fun builds but most of all relax and have fun. Don't care too much about the game, after all it's just a temp account for the 2 weeks.
Currently doing that right now and despite people get angry and toxic at me for doing poorly, I'm enjoying it. I don't say much in chat, just a "yup" or "ok" or "alrighty" every now and then. I don't know what it is but it's so therapeutic to not care, have fun and watch others get extremely upset about it. The best part is once the game is over, you can report them and know nothing can happen to you as long as you didn't say anything (or anything negative) in game.
League is a completely different game when you don't care, give it a try.