It is possible to keep several male gouramis in one tank, provided that you have enough hiding spaces and plants, and that your tank is big enough (count on around 30 litre for one gourami). Another important point is that you introduce fish of about the same size.
If you introduce your gouramis in stages, then change your decor around so the second gouramis is not introduced in the territory of your existing gourami. in this way both have the same opportunities to establish a territory.
If you want to have males and females, make sure you have a ratio of 1 male to 2 females. In this way both females get a rest and are not constantly harrassed by the male.
Good luck with keeping gouramis!