As Cheese Specialist said, a lot depends on what you have done before and what you like; however, for a generic opinion:
Livebearers (guppies, plats, swords, etc.) are typically easy to breed and fairly self-sufficient in the beginning- but is great experience for caring for fry.
Egg-layers can be fairly easy but often require some set-up of providing the right conditions and "nesting" surfaces. The fry are, typically, smaller and more fragile, hence requiring a bit more care on your part-- there are, of course, notable exceptions.
For the mating ritual, personally, I love the bettas. The nesting, mating, and final egg/fry care by the male is amazing. The initial trials and tribulations are much greater though- getting the pair together, separating after the ritual, etc. Too, overfeeding, fungus, etc. can wipe out the batch in a heartbeat.
Cichlids, especially mouth brooders, can also be great but may require a bit of set-up and after care.
I like all types - a lot depends on how much time I have to do the set-up, monitoring, and follow-up care. Good luck.