First, you need to grasp the game. Ask yourself what you did wrong. Did I last hit all the cs? Did I play right and not feed? Did I use my main champ or trying something new? Do I know the builds on this champion without searching on the internet?
I think the most basic part of the game is important. On higher elo, you need more advance Macro, Micro, and Map awareness to be a better player. Also another part is you need to use a high end pc (60+ fps is good) for a better movements in-game.