I would sujest a fire bellt toad,
they are easy to take care of
they have a long lie span
only need to eat about twice a week
one frog can live quite happy on a 5 gallon tank
and if you are lucky to get a male he will chirp for you.
last but not least they are just cool

If you would like more info on them and how to set up a tank you can PM me and i would be more then happy to help you and show you a pic of my set up.