This may sound 'old school' and seem dumb ay first but.....
There is nothing more colorful than a tank full of assorted damsels and a clownfish or two:
They are inexpensive...
They are very active...
They are almost bullet proof...
They come in a variety of colors...
They will not outgrow your tank!
I would put several of each: Yellow tail damsels (can substitute any blue and yellow damsel), Talbots damsels (yellow and lavender), 3 stripe dacyllis, domino damsels, and a Tomato or two percula anemone fish. Add a Royal Gramma and you have a beautiful mix of colors. Best of all, they are all 'reef-safe' and allow you to grow any coral you want without fear.
Yes, these are agressive fish but, if you add several of each, they will spread the aggresion out and no one gets picked on. There is constant activity and color in your tank.
Fish don't have to be expensive and 'difficult' to maintain to acheive a sense of accomplishment and a beautiful tank.