How big is the tank and are you going to be adding coral or not? Without this info its hard for me to suggest individual fish.
Clowns are cool for sure( especially some of the crazier color forms), but there are some REALLY cool fish out there that you may not see at first.
Dragonettes are really cool as well( on my list for my next tank), but can be finicky eaters and generally only do well in bigger tanks. also they are not compatible with some gobies( again depending on tank size.
My only regret with my tank is that i bought all of my fish before i really knew what the ocean had to offer.
My advise would be to take your time and find the fish that you absolutely cant leave the store without, not what you went there looking for.
As far as CUC, just remember they are animals and they need food too. unless you want to feed a tank full of snails and crabs, make sure to pace the size of the CUC with the amount of livestock in the tank.
Also, if your tank is small try and find fish that fill a role as well as add some flash to the tank. Sixline wrasses for instance are really cool looking (IMO
) plus they scavenge live rock and eat some types of parasites. there are some really interesting sand sifting gobies as well outside of the yellow watchman, or diamond, or the other common ones. So again do a bit of window shopping before you are shelling out cash.