SO MY DAD promised me he will buy me a new laptop (or computer) for my b-day (which happens to be on july4 )

well the thing is that:
IM NOT SURE WHICH LAPTOP I NEED D:
like.....Im going to go to the university ( im going to study digital graphic design)

And I know i need a powerful computer

with a really good graphic card (video card) D: but I DONT KNOW WHICH ONE!! D:
I like the idea of having a macbook air but...maybe a laptop with windows is the right one for me D: ....
HELP ME DECIDEEE!! D: pleaseee