Well you already have quite a few fish planned for your tank. Its best to slowly stock a tank so that the biofilter can keep up and your fish don't end up dying. You have a good start though, a trio of cory cats would be a great idea. They are fun to watch though hard to tell apart, I just use one name for all of mine cuz they look the same to me. A school of tetras looks great in any tank but they should have a school of at least 6 and the larger the school the more pretty it will look. Along with your gourami you already would have ten fish and would be at about the max your tank could have.
