I can always suggest somthing like a 1980-1985 Kawasaki KZ 440 or 305. it´s a lighter bike, but it has a good amount of power, and with 6 gears, the ratios are closer, which means more shifting practice as opposed to the 5 speeds. also, with the 440, it´s still classified as a light bike ((500CC) so insuring it is cheap, but it´s still got plenty of power. I learned how to ride on a 1980 Kawasaki KZ 440, and I learned well, I also still have it, and ride it from time to time. It´s a good bike to ride, even after the learning phase, you may even keep it as your main bike forever.