Keep the gourami alone for the time being, they are more than happy alone and if you end up with two male gouramis you might have a real war on your hands. A male and a female would be okay, however, if they actually breed then you may see a marked increase in aggression from the male as he defends the bubble nest.
As a rule, both danios and barbs prefer tankmates of their own kind. Ideally, you would want 6+ of each, but there is no way that many would fit in a 10 gal
. Rosy barbs can grow to 3" and danios to about 2"...so to have schools of 6 each, you would probably be talking roughly a 30 gal
aquarium. Any chance you could afford to upgrade to a bigger tank?
If that is an impossibility, then I would look to add another 2 danios and 2 barbs. That would give you 3 each; not exactly a school, but at least some friends.
However, you didn't mention whether this is an established tank or brand new. If it is brand new the tank still needs to cycle--and until it does, no more fish should be added. If that's the case, getting a water test kit and monitoring water conditions is a must.
EDIT: just went back and did my math. Even 3 each of zebras and barbs is still going to be way overstocked for your 10.
If I had to choose, I would at least get a couple more barbs, as they can be nippy towards other fish, but that decreases when they have mmore of their own. But getting a bigger tank seems to be almost a "must" if you can possibly do it.