I have 2 Orange storm clowns, and a neon dottyback in mine, and I don't think this tank will take more fish, in hindsight I wish I got a tailspot blenny to go with the clowns so it can pick at some algae on the rocks, instead I scrub it off every now and again.
2 clowns and a watchman goby(almost any shrimp goby)/pistol shrimp
2 clowns and any nanofish
royal gramma a cardinal and a firefish
Intermix those fish as much as you like, rainford gobys can be difficult in a new tank. Be patient with the cycling, I used Dr. Tims ammonia and Dr. Tims one and only to cycle, was able to add clean up crew after 3 weeks and after another 2 weeks I added the clowns.