Get plenty of guppies. They are perhaps the easiest fish to keep aswell as looking pretty (males). Just make sure you have at least 2 females to each male otherwise the males tend to nip each others tails. Be prepared to have lots of babies around in a few weeks
.
A couple of Black Mollies. These are what I like to describe as indicator fish as diseases are easier to spot on these than other fish.
A couple of swordfish. Nice sociable fish.
Neons/Harlequins - Very nice to look at in a shoal but don't tend to last too long and prone to getting eaten by larger fish (Angels/Gourami/Sharks). Nice starter fish though.
Zebra/blue Danios - Swift streamlined fish that are mainly top dwellers.
Plecostomas - Bottom feeders that will keep algae and a lot of fish crap at bay.
All the above will live happily together without too much care an attention in a well maintained tank. You won't need to worry too much about setting an acidic or alkaline ph level as they are pretty much fine in a neutral (ph7) tank.
Decorative 'show' fish:
Angel fish, while very pretty to look at are extremely territorial and are not recommended to place with small fish (neons etc) or fish with decorative tails (Guppies etc).
Silver Shark - Adds the cool factor to a tank "WOW you have a real shark!". Great fish but can get a little large in a small tank, much the same for red tail sharks.
Clown Loach - These look nothing like the marine Clown fish. Whoever tells you they do knows not what they talk about!
Guorami - Much the same as Angel fish (territorial, can be aggressive).
Kissing fish - Love to eat Neons - DO NOT MIX LOL
Do not buy kooli loach. They might look like snakes/eels in a bare tank but once you put them in your gravelled tank you wont see them again - they bury in gravel.
Best bit of advice is given above though. Do not be tempted to fill your tank up with fish until it has settled (2-4 weeks is normally fine). Introduce your fish slowly, do not just tip them into the tank, leave the bags to float to equalise the temperature. If you can, put them in a quarantine tank for a week before introducing them to your main setup.
I personally have never felt the need to pee in any of my tanks though, bit controversial that one lol.