personally I think gobies are the best for that size tank. And there are lots of gobies to choose from, little clown gobies or firefish, or a small watchman.
I have a 29 gallon with a clown, two firefish, and a bi-colored blenny
As far as a skimmer, are you looking for one that hangs on the back? I use a prizm deluxe, some people hate this skimmer but it has always done good by me. It is a lower end skimmer (cheaper) and it hangs on back, but it could also hang in a sump. The deluxe model comes with a chamber for running carbon (which I love because I don't run a filter on the tank) and a surface skimmer.
Have fun stocking your tank!