CS better and die less are the things I'd suggest after looking at your OP.GG page.
Go into a custom game and try to CS. Strive to get around 70-100 CS every time minutes. The benefit of CSing better is you get a ton of extra gold. The less gold you have in a game, the more you have to make up with your mechanics. So, the more gold you have, the more "mistakes" you can make without really being punished. Obviously you can still be punished, but if you are hitting for 200 while they hit for 100, you have to mess up a lot for them to outplay you.
After a few games, add in a few bots and try to win despite being at a disadvantage. Bots are easy to predict, but it will help you learn to take advantages where you can. If you ace the enemy team and aren't taking baron/dragon/towers/inhibs in your ranked games, then you're not using your advantage.
Learning to get carried is actually hard for some people. If you are 2/9 and you have a 10/3 ADC, sit on top of him and keep everything off him even at the expense of your own life. Or if you have a top lane carry who is ahead, help protect them. If you can learn to do that, you'll be able to win more games simply by enabling your team to carry instead of trying to solo carry when behind.
