I personaly don't use CO2, because It will cost me more money than buying ferts, and, ferts work just as good, for me that is.....but, there will be plants that will only grow with the addition of CO2, and, if you do buy thoes, i and don't want to make a DIY, or sped ALOT of money on a real system, i would just do more frequient water changes. (that will add CO2 into your aquarium.)
I would go with at least 1.5 WPG. (lighting) and, maybe 2-3 inches of sand, or, your favorite substrate, but, the largest i would use would be a little larger than a grain of sand.
the plants i would say, are:
java moss,
java fern,
christmas moss, any cryptocrone, any anubias, few swords, i would reccomend narrow leaf chain sword, i have that growing quite well in my 50 gallon. i think that is a good start on it. i would be glad to help you with any other questions you may have.
oh, i would also suggest some type of shrimp, i use red cherry shrimp ( Neocaridina denticulata sinensis) i think that is the correct name for them any way....and also Singapore Wood Shrimp are an awesome looking shrimp, filter feeders.
(there are MANY more plants that grow well in the low lighted aquarium, i'll add some more when i get a chance,or, you could just go to aquahobby.com, and look at there plant section, which, is an awesome list of plants.)