I don't want to sound arrogant or anything like that, but if you want to achieve level 12 you don't have to use any specific strategy or try to optimize your build order to the limit...
All you need is solid micro. Keep playing the game regularly and try to minimize your own mistakes. Knowing the ins and outs of each map and how you need to play certain maps can also help. This is something you can only learn yourself by playing a lot.
Good luck