I am 14 and about 150cm tall. i want a cheapish bike but not to cheap. What is a good dirt bike for me to start on?

A TTR125 is not cheap those are about 1200. Now that is pretty cheap for a dirt bike but I doubt you know how to ride a clutch. But if you think you are up to the challenge of a clutch then go right ahead. But i suggest something from Honda. Maybe a Honda CRF80F. Now those are clutches too but there easier to start on. That's what i started on with a clutch. I highly recommend that. Then i would go to a Honda CRF100F or if you grow faster then go to the Honda CRF200F those actually aren't that much taller than the Suzuki 125.