I agree with the above. Gourami and bettas are labyrinth fish, think of them like distant cousins that don't normally get along.
Not really a fan of bettas in community tanks anyway unless it's very well thought out, even then it depends on the behavior of the Betta.
You are somewhat correct about barbs and tetras. Some species will nip. Tiger barbs(all variants), skirt tetras(all variants), Buenos Aires tetras, phantoms, etc are all known to nip fins.
On the flip side there is plenty that don't nip. A trio or more of cherry barbs is a great suggestion and are very peaceful. Other tetras such as lemons, ember, black neon, silver tips, Cardinal, neon, Congo, Rummynose, and serpae are all good tetra species.
I think you overstepped a little bit with the shark. Thanks okay though, when I entered with hobby I wanted the same thing (and I did it because no one told me not to). I had a rainbow shark. Luckily mine was quite peaceful but once they grow up they can be territorial and aggressive. I would wait till you have some experience under your belt of how a tank runs and functions then you can dive into semi aggressive fish.
As far as gourami there's plenty of species there you could choose from as well. Large species such as blue, opaline, and gold gourami get 6 inches and I've heard can be a bit territorial. Smaller species might suit this tank better such as dwarfs, honey, moonlight, and Pearl gourami.
Just running some ideas through your head.
in the age we live in, your fish want list doesn't stop at what the store has, many locally owned fish stores can special order fish for you if they don't carry it.
Just to make sure.... Have you read about how to cycle the tank to make it safe for fish? This can save you a bunch of hassle and there is more to an aquarium than just fish and water!
Hope this helps
Caleb
