Started off with a 20 gallon and filled it with goldfish. During the summer they boiled so I decided to go for tropical fish; mollies, tiger barbs, rts etc. After one year I had upgraded to a 33 gallon (that at the time seemed HUGE!) and filled it with the same sort of fish as the 20 gallon plus angels.
In short, 20 to 33 gallon, goldfish to angels.