How to improve as a Pos 3 and what things could I have done better in this game

Match ID: 8752911070

Had a game as centaur earlier, I think I did pretty good for my standard but there's thing nagging feeling that I really missed a lot of things during this match. The feeling is also not exclusive to this match alone, I feel like I'm pretty prone to tunnel visioning and such and have trouble with itemization. Please help me.