Once you are done cycling the tank, get 2 or 3 male guppies and say 6 females. No reason to have to buy the rest, they will fill the tank in less than 6 months by themselves. For companions, I am partial to corydoras and would get about 6 all alike. They will not harm the guppies and are entertaining with their antics. They also help the way the tank looks by creating some action in the lower half of the tank.