I have a 29 BC, and keep seven fish. Two clowns, three pajama cardinals, hectori gobie, and a rainford gobie.
you’re definitely limited in space, and I wouldn’t add the fish all at once until you know how your filtration will react. These are also all small fish, with one of the clowns being the largest at just over two inches.
I’d also add them based on utility. The PJ’s are straight ornamental beyond the basic benefits of having fish on the reef, but I enjoy their aesthetic. The clowns I wouldn’t have added except that I inherited one and decided to get it a mate.
browsing live Aquaria’s a good idea to get ideas. See what you’d be looking at and what benefits they may add.