We started raising ducks last year, too. Without really knowing what we were doing, we got four breeds. We got two females and one male of the following: Indian Runner, Buff, Crested Whites, and Rouens. We got them from Metzer's, which sometimes throws in extra drakes when they send your order (we ended up with five drakes). If you order from an online hatchery, make sure you have a plan to deal with excess males.
We realized when they hit maturity that we had too many males for the number of females, so we culled down to just two drakes. To make life easier on the females, we chose the Indian runner drake and one of the crested white males (though we wish now we'd kept the Buff instead). Indian Runners are a lightweight breed, and Cresteds are a medium weight breed. We found it preferable not to have a heavyweight male trying to breed a lightweight female.
One or two drakes should be sufficient for the number of ducks you would like to have. if you are sure you don't want them for meat, I would get one or two Indian runner males; runners are very good foragers, and the females produce a lot of eggs.
At the bottom of my comment is a picture of our duck house for ten ducks and two geese and here is a description of how we built it:
Their run is fenced in and has two strands of hot wire, so they are protected from predators and don't have to be locked in the house at night. Honestly, they usually don't go in the house other than to lay their eggs. Even in the coldest weather they almost always prefer to be outside in the run. If you can give them a very secure run, you really don't need much of a structure for shelter. I built one like this around the edge of the pond and it's more than sufficient: