Dwarf gouramis can be very agressive. I had one in Germany before that killed my female and one here in the US in my 70 gal
that constantly bit me when I was pruning my plants. He even spit water at me one time and was the only fish that fought with my Kribensis male. That's when I had to bring him back to the LFS
. Also, he always bothered my Otocinclus and bumped into them, when they've been searching for algae on the glass.
If you really want one so bad, I would get 1 male and two female. Besides, females might be hard to come by sometimes. And as the other species you could consider honey gouramis (Colisa chuna) for example. They have bright colors too, but are more shy and timid and in my tanks they've never been aggressive before.
As for the corys, they love to be in groups of at least 5. They need the social contact, since they are schooling fishes in the wild. So the more, the merrier. Panda cories look pretty cool and they only get 1-1.5" in size. That means you can keep a lot of them lol.