If you dont have good micro and you wanna win with humans.. than just get more stuff than your opponent has. Or else you cant win, because your micro. So at the start of the game, early expand... Other than that, just have the right combo of units to counter what he goes.. you weren't that specific.

Headhunter $160 Grunt $235 Taruen $325, Beating a level 50, Pricless