I absolutely love guppies. If i were you I'd get two males and four-five females.That way there are enough females that the males shouldn't fight and they'll make your tank very colorful. They also have live young and breed year-round so id put some plants in one corner so when they have babies they can hide.
Happy Fishing!
(and if there is enough room still, id put a few neons in there for even more color. Thet'll school together and shouldnt bother the guppies)