Based on your needs, I agree with PumaWard. I think livebearers is probably the way to go in your case. They are very prolific breeders, and you will have many fish to add to your other tanks.
However, if you want to try something a little more challenging, I suggest Angelfish. Start with the basic silver angelfish, as they tend to be hardier than other varieties. I suggest getting at least 6 young angels, with the body size of about a quarter. Starting with 6 angels almost ensures that you will have at least one pair. They will grow quickly and will reach sexual maturity before long. As with most cichlids, they will choose their own mates. Prepare a seperate spawning tank ahead of time (preferrably a 20-25 gallon tall), making sure it properly cycled. Place long slender pieces of slate in your sqpawning tank, leaning against the side of your tank and your angels will almost certainly lay their eggs on it. I have also used extra large plastic Amazon Swordplants...the leaves are removable so I can move the eggs to a hatching tank with no problems.
Watch your angels for signs of a pair-bond. The pair will occupy a certain territory of the tank and they will defend it tenaciously. At this point, you should remove the pair and place them in the spawning tank, so they will spawn without worrying about having to defend their territory. You will need to decide if you want to raise the fry artificially in a seperate tank, or allow the fry to remain in the tank with the parents.
The eggs hatch in about 48 hours, and reach the free swimming stage in about 7 days. You can raise the fry on baby brine shrimp.