What is your goal for breeding? Eggs? Meat? Show? Just because?
Harlequins, Khaki Campbells, and Runner ducks are all good egg producers.
Pekins, Muscovies, and Rouens are great meat birds.
For showing you would want to find a breed of duck you like, find a show breeder with proven quality lines, and go from there.
If you want breeders just to breed ducklings, then find a breed you like and go from there.