Hi
If you are a beginner I would suggest 2 hens together. If you get a pair you are then setting them up for the next breeding season. Research would be needed for the breeding such as feather type when pairing, food requirements etc.
As finchly said for a cage only 1 male. I have an aviary with 3 males happily living together with the hens. I also do put several males together in a large flight cage at times and they do get on. For simplicity stick to one male.
Are you looking to breed? Will these be your first canaries? Canaries are very sociable mine move around as a flock.