Dwarf Gouramis do not school, and very often they are downright hostile with on another. Most of the Dwarfs you will find in stores will all be males since the females are not pretty. I would not put more than one Gourami per foot of tank width and make sure you have a lot of plants. If you try to breed them, search around for a place selling females, then setup a tank just for breeding and read up on how to get them to spawn.
Dwarf and Tiger Barbs do not get together all the time. The Dwarf are flashly and slow (compared to the Barbs) and can be an easy target when they start to defend their territories.