It's possible to keep up to 2 males or a male with 2 females. A pair sometimes works but the male might bully the female.
I actualy would suggest honeys as a better choice. They are almost as colorful as the male dwarfs but slightly smaller, much hardier and you could easily keep a trio, even 2 males and 3 females, perfectly peacefuly.
The most hardy gouramies though, are the three-spots which also come in opaline, gold, cosby etc color morphs. The downside is that, males especialy, can be very aggressive - to the point where males (usualy of the same color interestingly) will fight to the death. They also have the disadvantage of being big at a max. of 6" so you would oly be able to realy keep one. They are still excellent gouramies to start off with if you want something indestructible (well IME anyway) to start with.
Other gouramies I would suggest are the banded (colisa fasciata), the thick-lipped (colisa labiosa) and the pearl/lace gourami. The first 2 get to about 3-4" and have a similar temperament to the dwarf gourami and also similar coloration.
The pearl gourami is my absolute favourite and could prove an excellent choice. They are one of the few gouramies I would not be worried about keeping in a distorted male to female ratio (2 males, one female for example) - though there are exceptions and I have known fish that will attack all other gouramies (only one actualy

) as well as mature males that will peacefuly live in a group of 3 in a 20 gallon. These are almost as hardy as three-spots and get to around 4-5" but are incredibly beautiful fish. A pair or trio would work.