No need to apologize--it's good to kick around ideas, and you've come to the right place for advice. The basic rule is that small tanks need small, not-too-active fish. And with most fish, what matters is the footprint (size of the base) more than the total gallons.
Since a 15 gallon high has basically the same footprint as a 10 gallon, you're fairly limited, but there are some cool options. I've never kept honey gouramis, but seriouslyfish (my most trusted source) recommends a bigger tank for them. Since Walstad tanks need to be under-stocked, I would advise against them. Guppies might work.
@emeraldking is one of our resident guppy experts, so perhaps he can comment on that. But a 15g is really quite a small tank, so don't be afraid to think small. One nice school of microrasboras (there are many different kinds) and a few shrimp and/or snails would look beautiful.
To my way of thinking, animals like snails and amano shrimp don't add much bioload because you don't feed them much; they simply eat what's already there. So you could add a few shrimp or snails easily enough.
Aqadvisor.com is good resource for playing with ideas. It isn't perfect, but it will at least keep you from getting overstocked.