I would say any of the big four manufactures, Honda-Cr, Kawasaki-Kx, Suzuki-Rm, and Yamaha-Yz. I would say the most popular freestyle bike would be the Honda Cr-250r with an aluminum frame, but really all the 250's would be a good choice. Now in your price range a 125 would probably be more in-line with what you could find. Which depending on your skill level could be the better choice. I would look for the newest bike in the best shape, and ask questions of the seller on his maintenance practices. This could tell you a lot about the condition the bike is actually in; such as things not visually seen. A lot of people shy away from bikes that people raced, but racers tend to take better care of their bikes than the average weekend warrior. Most importantly get some quality gear to go with the bike. Hope this helps