Hi
There is a large variety of submerged water plants and some will grow in any situation.
There are floating as well as plants that attach to rocks or wood . Substrate is not necessary. Java moss and fern as well as Anubias must be planted this way.
For rootted plants probably the easiest substrate is 2/3 mm gravel . Many types will grow in this quite well.
Light is the limiting factor the more light the more choice. 5 watts per gallon is probably ideal but again many will do quite well on a lot less..
Size will be the biggest problemm in a small tank. But even that isn't too much of a problem Just root some cuttings when they get too large.
The gourami and Cories are good choices for a planted tank.
The main method is to decide what type of plants interest you and set it up with those guidelines.
A planted tank can be as much or as little work as you want to do. gary

As Garyfla stated I would go with Java Fern or Anubias which come from Africa. There are several types which grow from 4 to 8 inches tall. They do well in low light conditions and do not need expensive extra lights.

Anubia's grow slowly and will not take over a small tank like some other plants will. These plants are not bothered by the types of fish you have and Java Fern being a fern tastes terrible to plant eating fish.

I have bought plants from sellers at Aquabid.com, you will find some great plants there that would be hard to find locally. Plants are cheap to ship because of the light weight so go for it.