Get a ten gallon tank, fill with water and treat for chlorine. Cycle the tank and add guppies= babies. Oh and feed them lol. Any of the live bearer fish (guppies, mollies, platys, endlers, mosquito fish) are very easy to breed. Just put them in water and it's done, that easy. Live bearers are easy to sex, the male has a pointy anal fin (like a pin) and the females anal fin is rounded. Depending on your tank size there are plenty of other fish easy to breed, guppies are suitable for a 10 mollies and platys arent, I'm unsure on endlers and Mosquitos. I know convict cichlids are easy to breed but I'm unfamiliar with the tank requirements. From my experience most fish will readily spawn in an aquarium provided you have it setup to meet their needs, this can be as simple as a ceramic pot on its side for a cave and having clean water that's the right temperature.
