Which fish species will do fine in aquarium without plants?

It would be easier to ask the question the other way around. Almost every fish will live fine with fake or no plants.

Most fish will thrive in any tank, as long as it's properly cycled and maintained, and of adequate volume. IME, there are a few fish that will not do well in an unplanted tank, so the shorter list is: Algae obligates, like otos, and some cats/plecos. Straight herbivores can usually be fed appropriately from commercially available foods, but some really do better with natural plants instead of commercial preparations or vegetables.

What fish are you interested in keeping?

Both will be fine without plants. You will need to provide some decorations that will provide cover for the fish, of course, but they can be wood, resin aquarium decorations, fake plants, rocks, etc. For gouramies, you'll want to provide cover that's near the surface, as they prefer the surface areas, while tetras tend to hang out mid-water.