Well, there is no "right" answer to that question. The general rule is one drake for every 4-6 hens. However, there are always exceptions. Some people have to have even MORE hens, and some people less. In my adult flock, I have two drakes and two hens, and for us, it's worked out perfectly. One of my drakes is much more laid back, and they never seem to fight over a hen, and neither of the girls seem overbred or picked on. We do now have 4 new ducklings so we're hoping to add more girls anyway. That way when one goes broody and sits on a nest of eggs, we aren't down to one hen for the boys.
So in the end, it just depends on your flock, and how it works out. I wish you the best though!!