Glassfish, at least the species commonly available in petstores, are typically a light brackish water fish. Not going to be compatible with cories or tetras.
10 gallons is a bit small to work with.
Let me suggest that, if you can lay hands on them, Honey Dwarf Gouramis (Colisa chuna) are a better bet that even the regular Dwarf gouramis (C. lalia [Actually, they may both have been reclassified back into Trichogaster, but I lost interest before researching it, as I am sure you are doing right now.... so]). 1 male and 2 females is a good number.
People stress the shoaling aspect of cories more than is profitable in my opinion. You won't get real good shoaling behavior without 8 or 10 or more, so don't sweat that. On the other hand, go with one of the smaller cories if you can lay hands on them. C. pygmaeus, C. hastatus, or C. habrosus all are right around 1". If you plant the tank well and keep up on your water changes, you could stick 8 or 10 of those in there. For he slightly larger species, I'd recommend a trio of C. metae, ususally traded as Bandit cories. AVOID Emerald Green Cories (Brochis splendens), as they get nearly 3" long. Ditto the albinos (Female bronze and Paleatus cories can get nearly 3").
If you can lay hands on them, there's a really pretty little catfish that's just starting to come in from southeast asia: Hyalobagrus flavus
. They're cute as a bug's ear, stay small, and tend to be more midwater than most cories. I'd go with 6 of those or 10 if I were just doing them and the Gouramis.
To round it out, rather than a tetra, why not go with something that will feel more natural with the gouramis? Emerald Eye rasboras, or one of the pygmy species like Bororas maculatus would be a really nice complement with a school of 9 or so Emerald eyes or 10 or so of the microrasboras.
If you do go with the tetras, yeah, 6 or 8 neons would work. Might nip on the gourami's fins, though.