i would get the 5 gallon tank kit from walmart. then get a fluorescent bulb for it. (they sell it in the same isle)... as far as fish go, you could probably put plants in it, and get a couple shrimp (3-5) and have them in there, or you could get a couple guppies, and a couple of shrimp.
i have a 5 gallon tank on my desk, its moderately planted, i have 2 male guppies, 2 LARGE ghost shrimp, and 1 indian dwarf puffer.