It's actually really easy to sex honey gouramis at any age since males are the colorful ones and females are dull. There's a very good chance that you won't be able to find a female in stores since most people don't want to buy them because of their grayish coloring. I was lucky and saw a female in the tank that I got my red honey a few days ago. Didn't get her, but it was a cool find!Ditto on the honey gourami. I would aim for a female, granted the ones in fish stores are probably too young to sex.
I have a female in my twelve gallon tank and it has never shown any aggression. Just make sure you have a place for it to hide, and they also appreciate plants for cover and to nip at algae.