Do you mean this tank:
30 gallon - 2 angels, 2 cories, 1 female guppy, 1 fancy tail male, 1 male betta, 1 fancy tail female?
If so, you need to be aware of certain things before considering new additions.
First of all, male bettas and male guppies tend to not get along. This is because bettas tend to mistake male guppies, with their long fins and bright colors, for rival male bettas. The result is generaly dead guppies.
You also have to keep in mind that, once mature, if your angels turn out to be a pair, particularly if they choose to spawn, they will take over the tank and become rather territorial. At this point, your betta is likely to lose a lot of fins, possibly even be attacked and killed. Remember that he is also territorial, so the angels and betta will be competing.
Small fish always stand a risk of getting eaten by large angels so the guppies (most likely the male because they tend to be smaller) are at risk.
As for adding gouramies, you already have one in there - bettas are gouramies. Having said that, I'm shure you'll realise that the word 'gourami' describes many species so answering your question isn't a simple yes or no - or at least it wouldn't be were it not for your betta.
Because you already own a betta (and are limmited on remaining stocking room anyway), I would not suggest adding any more gouramies. Bettas and other gouramies don't usualy get along. Fights break out over territory, the angels'll get pulled into it and your tank will no longer be peaceful. It's very likely either the betta or new gourami would end up dead.
If you want to add something to your tank, I'd suggest a few more cories. You'll actualy be pretty much fully stocked if you were to add 2-4 more of the catfish. Keep in mind that cories are schooling fish and like to be in kept in groups - 4 minnimum is the usual reccomendation.