Dwarf Gouramis can be quite aggressive, even in a large tank. You could have 1 male and 2 female dwarf gouramis, but females are not often sold. You have a few options for schooling fish. You need fish that do not need length, so angelfish would be nice. I have a pair in my tank with honey gouramis and have no issues. You could go for a pair of angels, a pair of smaller honey gouramis, or maybe a pearl gourami. A few cories would be nice. A smaller type like pandas or juliis would be great (8 of those maybe) You would probably still have room for a small school of tetras. Glowlights, neons, cardinals, lemons. There are plenty to choose from, just make sure you do not get anything to active, that is going to need the length.
Sorry, I cannot really help with the number of gouramis, all I know is some can be fairly territorial, and I do not want to give you the wrong advice
Why not give us some suggestions of the kind of fish you are looking for, as you may like different species?
Hope this helps!