I would start with the propeller, the size requirement to generate the required power (power need is probably pretty low) and speed ability per expected wind speed. I would figure that out, the drive requirement falls easily out of that. Mind you I have no clue how to start figuring out power ability and speed ability.
I believe you have to go the other way. Somewhere the generator has a power curve where you can find peak power, and maximum rpm. If you input too much power it will overspeed, if you dont have enough power its likely worthless. The correct propellor would produce peak power at mean average wind speed, and allow the generator to reach max rpm at a point where the blade tips stay sub sonic. Most wind electrics start feathering out of the wind around 45 mph to keep peak rpm constant, and at some upper limit, and after its fully feathered, they apply a brake. The correct prop would dictate the general gear ratio between prop and generator.