I would recommend a pair (that's not to say a breeding pair; they can be of the same gender and unbonded). They are very much flock birds and do a lot better with at least one of their kind, in my opinion. There's a chance but not a big one that they will get along with your other birds. A single pigeon would (most likely) either be lonely and depressed or get way too attached to you, which isn't healthy. You really need to think this through though - in my opinion adding a pigeon is harder than say another lovebird. On the one hand they're a completely new species with very different needs, but they're not like parrots in that they climb and chew and play a lot. Instead they need a lot of room to fly, as much as possible. It's their main form of enrichment, generally speaking. That also means big cage, which needs to be set up specifically to work with their wingspan while still having enough interesting stuff in it. So what I'm trying to say is, it's a big commitment (as is any bird, but this will grow your flock significantly if you get a pair) and as it seems you're a minor (like me) you need to carefully think about how you'll be able to keep them all through things like college, moving, travelling, whatever is in the cards for you. It's always good to think about for example the possibility that at some point your parents will need to take care of your flock for you perhaps for a week or maybe longer.