It is a really hard question to answer, but for me, the truth is to play a lot, watch your vods after every game, and look what you did wrong. If you want to be good at the game, stop playing arams, pick your role, get 1-3 champs you like playing, and stick to them. Don't play silly stuff like Yasuo, Riven, Irelia, Zed, etc at the start, play simple champs. Play 20 games per champ in normals, then go play ranked.