SOO CONFUSED! Whats a good dirt bike to get now?

okay so im basically sick and tired of my old bike i mean i've been riding it for 3 yrs now and i'd really like to get a new bike for my fourth season! Sooo, im thinking about the crf150r expert cuz im thinking about racing next year...or a friend of my dads who use to race supercross said i should get a 250 because im good enough. but that would mean i would have to shave the seat and get a spring kit to lower it (im like 5'3 so yeh)
whut do you think i should do.