Welcome to Planet Catfish!
Although i am extremeeeeeeeely biased i'd suggest a tanganyikan set-up for
- they are small,easy-to-keep, nicely patterned, readily available, not too expensive, active, peaceful, hardy, gregarious & best of all, fairly easy to breed, with a good market for the offspring - what more could anyone possibly want???
Of course it's really all about your preferences & budget. Mats makes some good points for searching but alternatively, look through cat-e-log & see what you fancy, read about them then ask specific questions in a thread here. (as a crude guide, if there are limited pics in cat-e-log, the specie might not be readily available).
Keep us posted
