Livebearers (only buy the same sexes though unless you want tons of babies) are good, hardy, peaceful community fish and a good beginner fish. Some more hardy fish are within the Tetra Family (common ones are neons, glolights, or blackskirts). Most importantly it depends on the size of the tank, most tetras prefer to be in schools of atleast 4.
Good luck and welcome to the forums!
I started with platties and mollies, then added some tetras.. they are so peaceful and easy to care for.. but quite fun to watch too. I've had my community tank now for 5 months and am now getting the itch for a second larger tank!!! Almost convinced my husband that it would be a great idea.