The tank's size and what else is in there will determine what you should or should not keep. Let us know.
If you don't want gouramies that will breed, don't go for the three-spots. these are the easiest and will breed very readily - even in relatively poor conditions. Though dwarfs will also breed quite easily, they are less likely to do so successfuly.
Having said that, you may want to consider a different gourami as dwarfs are rather fragile and prone to disease. females can also sometimes be quite hard to find.
Some other factors that might influence your decision are aggression and sex ratios:
If you were to go for three-spots, like Miss Dib Dabs said, they are likely to terrorize their tankmates and males are especialy aggressive and territorial. 2 males in the same tank are even likely to kill each other and I personaly would not keep fewer than 3 females per male. Having said that, an all-female group is an option but you'll want to go for 4 or more females to spread out hierarchical aggression - 4 females would, in turn, require a 40 gallon tank minnimum. Over-crowding gouramies is unwise and very risky.
If, on the other hand, you went for dwarfs, males can co-exist relatively peacefuly as long as they have about 10 gallons each. It's also best to go for 3 or more males, again, to devide any aggression. As such, a 30 gallon is required. Having said that, an all-female group also works and females are peaceful and quite social (in fact, I wouldn't keep a female dwarf alone) so the number won't matter but they are not as brightly colored as males so most people wouldn't go for this option. Keeping a mixed group also works fine if you have 2 females per male and provide 5 gallons per female + 10 gallons per male. A 20 gallon will hold a trio perfectly.
Having said that, male gouramies will do fine on there own though I would not keep a male three-spot in a peaceful community anyway as he's likely to start killing off his tankmates once mature.
Like I said in the beggining, I'd suggest going with a different gourami species altogether...
For larger tanks, pearls (trichogaster leeri), banded (colisa fascita) and thick-lipped (colisa labiosa) all work well as trios. They are all peaceful towards tankmates but males are still a little territorial. You can also get one of each and they should get along fine. Again, 10 gallons per fish is a good guideline to go by though you could keep a trio of any of the above in a 20 gallon as long as you are careful to not over-stock. Pearls get to 5", bandeds to 4" and thick-lipped gouramies to around 3.5". The 2 colisa species can be sexed based on color as males are brighter than females and these two are closely related to dwarf gouramies so much of the info on dwarfs applies to them as well - only they are much hardier than dwarfs. The pearls are similar to three-spots but also, IMO, the most peaceful gourami and sexing them is extremely easy as males develop a stunning orange-red underside coloration and a very long, pointed dorsal fin and extendd anal fin rays. Females are also beautiful but are lighter colored and don't have the extended rays.
For smaller tanks, honey gouramies (colisa chuna/sota) are the perfect dwarf substitute. They are similar in appearance though the color is honey-yellow with some red color morphs also available and the males develop a blue-black throat area when in breeding condition. Females are duller and often translucent. These stay a little smaller than dwarfs, reaching only 1.5", and a trio could be kept in as little as 10 gallons. Males are still territorial but honeys won't harm their tankmates and usualy will also ignore other gourami species. They are much hardier than dwarfs also.
None of the afformentioned fish are likely to have surviving fry if bred/raised in a community tank as any fry/eggs will get eaten by tankmates and, once the fry are free-swimming, by the parents themselves. Having said that, the easiest way to prevent any gourami from breeding is simply to have a strong current near the surface of the water. this will not allow males to build a nest in the first place so there will be no spawning. If you want them to show nesting behaviour but don't want the aggression that comes with it and don't want eggs/fry, just destroy any nests when they appear. the male will re-build it but you can just keep destroying it until he gives up. Keeping the temperature at around 77 deg F will also discourage most gouramies (though not three-spots) from spawning as they preffer higher temps of around 80 deg F to breed.
edit: for 4 spelling mistakes
, if they do breed. 
