Crested Geckos are nice.
I have a crested gecko (obviously ) and they are one of the nicest geckos you can get! They don't mind if you hold them a lot and they are simple to take care of.
Cresteds are the best choice for you, IMO. They don't need heat, eat CGD and don't REQUIRE insects, are easy to handle, cute, and they don't have to be expensive.
But if you can foot the bill, leachies are hands down my favorite... they're like big, eccentric cresties.
I'd go with the 20 or 30 gallon. No, they don't need UVB. Cresties are noctournal. A heat bulb will be ok if it gets a bit cold.