What kind of fish do you want? Hopefully you don't want larger fish as those will quickly outgrow your tank. How long has your tank been running? Assuming these are the first fish you are putting into your tank consider Cardinalfishes, or chromis. You can even do a couple of percula clowns they don't HAVE to have an anemone to thrive. Go with smaller fishes so you can have more differing species. A rule of thumb (and it's a rule of thumb!) is 1 fish inch for 2 gallons in the tank. So theoretically you can have 12" of fish.
That doesn't mean you can have 1-12 inch fish though! But you can have say 3-3 inch fish and 2-2 inch fish. Find out how large the fish will get.......most sites give you the shipping size not the mature size. Look at nano fish then you can get more for your space.
Good luck!