Many people on here have critter keepers. They are really good. You can filter and heat them. Get a Large.
I reccomend a MARINA Goldfish Starter kit (Its about 3 gallons) And it comes with EVERYTHING. Plus its 20$. In total, its problably cheaper than a Kritter keeper since you have to buy all the extras in a Kritter Keeper.
*2 Bettas (for now RIP Ryu) *2 Goldfish *9 Guppies *1 Gourami *2 Chinchillas *2 Budgies *2 Dwarf Frogs *1 Dog *1 Cat *2 Hermit Crabs *2 3gs *1 10g *1 Pond *2 2gs