What is the best dirt bike for a beginner at 150lbs and about 5'11"

I've been mountain biking as long as I can remember and I know that moto is completely different, however, I've always been on a quest for speed, I ant to get myself a dirt bike that fits me, even though I have never been on one, I want to know what bike to get for a beginner that will last me at least somewhat high into my skill