IMO, all that comes from experience. Just play the game and enjoy it as much as possible. Don't think too much about scores but don't throw games as well. You don't have to play EVERY champion, just have a wide diversity of the different types of champions. Also, I don't suggest spending most of your time playing against AI.
Every once and a while just pick a new lane/jungle and try different champions. Eventually you'll pick everything up. Because in LoL, there's a lot of champions that play & resemble other champions. Watching streams is a good way to learn some combos, patterns & routes.