I am sure we can help you there! Have a good look around the lfs and on the net etc and write a list of all the fish you like then start checking their needs.
Firstly though do you know your water hardness? Much easier to have fish that naturally live in the same water hardness as your tap water saves a lot of hassles and the fish really do well in their right environment. So water hardness, PH and temp will determine from you list what you can get then you will need to go through temperaments and assess if they can live together!
Sounds long and difficult but it can be very rewarding when you know you have the right mix and they are getting the very best of care from you!
Catfish if you follow that url you will also see what PH and temps etc you would be looking at keeping your tank then you find other fish that can live in that water then find out if they can live together (from us) AND YOU HAVE A TANK FULL OF HAPPY FISH!