I think 2-3 units and a hero are a good number for your first game.
If you don't use machine guns in your first games, you can keep the units very small (say 5-8 models) and fasten the game this way. I think thats better then starting with a maximum of models and units for the beginning.
The hero will be very tough compared to the units but this way you can try and use his special abilities without to much risk!