I'm certainly no expert, but I can tell you that most reptiles aren't very easily cared for, nor cheap -- they require a certain level of heating, humidity, etc. Not only would you need the tank, but [depending on the type of reptile] you may need two thermometres, a heat pad, a basking light, a nocturnal heat light, a UVB producing light...plus special food and all of the other equipment that you need for a reptile. Also, a ten gallon tank is not suitable to most reptiles. There are some that are dubbed "easy to care for" but that is usually only when compared to other reptiles. If you want to compare reptile care to cat care, a reptile would be very difficult compared to a cat because with few changes some reptiles can die so easily . That being said, I've always heard that corn snakes are cheap and easy to care for -- only my friend had two that both died within a week.

As for amphibians...How about an aquatic frog? I hear they are fairly easy to care for. You can find them at pretty much any pet shop. I once had a small toad/frog (not too sure) with a newt, and they didn't take much effort, although I never cared for them properly. They hated to be held though.