I would start with montipora cap and montipora digitata corals. They are cool looking, hardier than most and grow fast so you can usually find a frag of one very cheap.
As with all corals you will have a better shot if you get a frag from a friend, so you know the coral was tank raised, and not from the wild. Wild corals in general sometimes have a ruff time acclamating to aquariam life.
HTH,
Whiskey