Bubble issues typically stem from closing the air too much. Think of the pump as doing 180 gph, you set how much is air and how much is water, as you choke down the air, water flow increases, the bubbles move further and faster and more exit.
Assuming you are using it in the stock position, pump intake facing the deflector, and you have the blue sponge bubble trap installed. If you set the skimmer with the air all the way open, work with depth first (marked water line is the maximum, it can be set so this line is up to 1" above the actual water line) then close the air as little as needed. Always keep in mind that a small skimmer will never realistically skim dry, dry skimming requires height to dry the foam, so set it so you get something about like light iced tea.
Also, keep in mind water chemistry will play a big role, substances known as surfactants, generally organic additives, stress coat, dechlorinator, etc, and likewise non phenol free floss/pads (if you use anything not specifically made for aquariums, this is probable) and organic scavenger resins, will all have this surfactant effect, they make the water more "slippery" and bubbles travel much further. A very high DO or CO2 level can also cause bubbles due to degassing in the skimmer. A KH over 14 or rapid growth of algae/soft corals, can cause bubbles for this reason.
