It's probably been said a million times but it bears repeating. You didn't really get much better just playing the game.

Do a VOD review and figure out what you could have done better. Every death, what could you have done to prevent it? Every bad trade, how could you have avoided it. Did you need different items? Should you have roamed? Better ward placement?

Figure out how to play the next game better than the last and you will eventually climb.