Beta fish are very neat to have. Only problem with them is they are very very territorial. You cannot put two together they will kill one another. They also breathe above water so there is no need for live plants, bubblers or filters (unless you'd like them) they are pretty clean mostly also don't eat much.
Beta fish make good pets especially for beginners. They are pretty and very very hardy and easy to care for. With the ability to absorb some air from outside of water they can live in slmething as simple as a fish bowl. Also they are very cheap and easy to obtain. Sea monkeys on the other hand can make good pets also. They require a bit more patience though. They don't grow very large and sometimes it can be tough to get them to hatch at all but if youre willing to take the time to raise some they can be pretty cool as well.