How to improve?

So, I was crushing it this game, which I don't normally do, and I was wondering how to play the game well enough to get an S. Even an S- would be cool. I went 11/0 which was okay. I clearly needed to up that number considerably to be a top player. My CS probably needs improvement too. With only 130 in 20 mins I feel this is too bad to be a top performance. I don't normally do this, (because I'm bad) but I even bought a this game. Should I pick up a second one? Place more ? I want to stress I'm usually way worse than this (see bronze scrub lord) and I was hoping for some advice next year when this happens again, so that I can pick up the fat S.

Thanks, Puddle