What is a good beginner dirtbike?

I would go with a KX500 or CR500. If you can find a 370 Can-Am that also would be good.

Perfect bike for you would be a Honda CRF250X or a Yamaha WR250F. Both are suited for trails, and both don't have as much power as MX bikes. Suspension is smooth and power is smooth. Perfect for a beginner at your height and weight. It will also be fine on an MX track if you ever want to. I own a 2005 CRF250X, and when I rode it, it was extremely smooth. Very easy to ride. I now ride a 2012 Suzuki RM-Z250 and the difference between the two is immense. The MX bike is a lot more challenging to ride than the X, which is like driving a tank. Which is very good for beginners. The X or the WR are both very stable, and easy to control. 2 strokes are not good beginner bikes. They are snappy and get their power at high RPMs. Beginners tend to go quite slow, which doesn't match the personality of a 2 stroke. 4 strokes have a lot of bottom end, or power on low RPMs. Good luck.

Yeah i would stay away from a two stroke not the best bike for a beginner. If i were you i would get a wr250f, ttr230, or crf230. I starred on a ttr230 i thought it was a great bike. Perfect for the roding you want to do. But if you have ro have a two stroke get a 125. You can learn on that too its just a little more difficult