Normally a good ratio would be 1:1 or 1:3.
It really depends on what the fishes attitude is. A pair of the same species will probably go good together. But then again, if one female is being harassed by a male (male wanting to mate all the time), try getting another female to take the stress off.
The harassment in gouramis isn't all that common though. The female normally gives the signal when she wants to mate.
So yeah, just see how things go, and if the female gets nipped a bit, get another female to take all the stress off of the one.