Extremely obvious, but just keep practicing, and find people to play with in league, they will help to push your growth. However, you need to practice on your own in solo queue, since this will give you a large variety of experiences with different weapons and playstyles, that you will need to learn to counter.
I also recommend that you choose a role, or weapon to keep practicing. Consistency with a weapon or role will help you understand the game more easily, since you fit into the game the same way almost every game (excluding strange team compositions). Focus on little things every game to improve on, like getting your special maybe 15 seconds into the game, or check certain flank routes every game. Use the app to keep track of little details, to see if you die too frequently, or need to be turfing more, etc.
tl;dr: Practice, practice, practice, strive for consistency