Depends. The tiger barbs might be a problem but if you get one of the more robust gouramies and get a few more tigers at the same time you might avoid confrontations - at least for the first couple of weeks or so. Later, having a well-planted tank with lots of hiding places and especialy some floating plants will help further. How many gouramies would you want?
In a 33 gallon with tiger barbs to contend with, I'd go for a three-spot male. You can choose from any of the three-spot color morphs - the natural blue, cosby, opaline, gold etc. The reason I say male is because he'll get a little larger than the female and would be more territorial so the tiger barbs would eventualy learn to keep their distance once he's established a territory. The downside is that male three-spot gouramies aren't too good with other gouramies so just keeping him is best. They get along with most other fish though (just not gouramies). If you were to get females, you could keep two or three. However, keep in mind that they can still be quite aggressive and as they get to 5-6" you need to make sure they have plenty of hiding places and not over-stock.
Another possibility might be a moonlight gourami though these get to 6-7" so you could only realy keep one, or possibly two, comfortably. They aren't as aggressive as three-spots and might be a little more prone to being nipped by the barbs but a big school of barbs will usualy occupy itself and won't harass other fish as much anyway.
I would avoid pearl gouramies because of their long fins and you probably should stay away from small gouramies such as sparkling, croaking or honeys as they are likely to get bullied by the barbs. Dwarf gouramies MIGHT work but I wouldn't risk it because they are prone to disease if they get stressed by the barbs chasing them. Thick-lipped or banded gouramies might work ok though. I assume they would be ok if the school of barbs is large enough to occupy itself (7-10). Just make sure you don't over-stock as 10 barbs would mean your tank is almost fully stocked.
My prefference would be for a single male three-spot (or any of the three-spot color morphs) and also add 2 more barbs, 2 more danios and 4 more white clouds. That would see your tank pretty much fully stocked.
