Whenever I get new ducks or chickens, I like to get more than one. I feel that my ducks are happier when they have friends. In my experience, my birds are happier with friends. But it is up to you if you want to get more ducks. More ducks require more time, care, and money. If that is something you want to do, and are fully prepared to care for the ducks for as long as they live, then get more. The duck you have now might be happpier. Bringing in another duck while your current duck is a baby should make the introduction process faster, smoother, and without potential injuries. But please keep in mind that this is my experience and opinion.