In general i definitely recommend buying used. For those criteria specifically I'd recommend looking for a used Honda Rebel.
If you're open to naked sport bikes with a more upright riding position you could look at cb300, z300, mt-03 which should have pretty reasonable insurance rates as well.
Also kind of depends on your size as well in my opinion, if you're 6'6 320 a 300cc may feel a bit anemic even as a beginner. Regardless I'd recommend erring on the side of smaller displacement for your first bike. While it's true that at the end of the day it does all come down to throttle control, a smaller cc bike will provide a wider margin of error as well as being lighter and more maneuverable.