How much live rock do you have? How many and what types of fish you want to add depend on how much filtration. Clowns are always a good choice. They are Hardy, friendly(in pairs), tank raised will eat most pellet/flake/frozen meaty foods.
Most of the Damsel family are easy to care for, though they do stay small. They can get quite territorial and somewhat agressive. Avoid Domino's. THey get big(my 2 are 3" across nose to tail, and i've had em 6 mo), and are qute aggressive. They have chased 2 of my blue damsels completely out of the tank. WHen i setup my new 125, they arent going.
Gobies are fun. It really depends more on the flavor of your tank. Do you want aggressive tank, moderate, or passive. Most of the fish you have are docile to moderate. Introduction of say a Lionfish, would result in many losses.
Though they are cheap, I love damsels. They dont get as big as some, but they are quite active and come in many colors. If introduced into an already stocked tank like yours, the aggression wont be too much of a factor. Most stay under 2"