im just starting dirtbiking and im 13 years old and i was wondering wut would be the best type uv bike for me like a 125 or wut. im about 5 foot 7 inches and im a fairly big guy, i have ridden before but only a few times wen i was like 8 butnot much, my step dad rides and hes gunna get me a bike and i wanna know in ur guys opinion wut size would be best for sumone like me