What dirtbike should I get?

Your best bet is a 2 stroke for no to low maintenance. You wont have to worry about out growing a 250 2 stroke, Im 23 and 230lbs and my yz250 will still let me know who the real boss is every once in a while. 250 four strokes are slow and the 450 are great until something happens and you have to take it to the shop, so unless you know how to work on 4 strokes Id go with a 2 stroke. 2 strokes are easy to work on and deliver more then enough power. plus 4 strokes are heavier.