hmmmm....
There are quite a few plants, Anarchis, Onion plants, are used in ponds sometimes. And if im not mistaken they will grow flowers.(im not 100% sure on the onion plant)
Umm what else, you can get some Java moss, Red tiger letus looks like underwater
lily pads. Then you could get some floating plants if you'd like. Duck weed, Water lettuce, ect ect.
Co2 injecter all depends on the type of plants you'll be getting.ferts also depend on the plants, but Im sure they'd love some . Substrate is important, you can go with a very good substrate made just for aquarium plants, or you can simply buy the normal bags.What type of fish does this tank hold? Personaly i would go with a very fine substrate like sand, or small gravel. Nothing bigger then pea size. The bigger the gravel the less nutrients the plants could take from it.
Now lighting also plays a huge role on all of this. You should have a flourscent light. The main rule is 3wg. 3 watts per gallon. But once again it all depends on the type of plant.
Good luck.
(BTW, Heres a good link,
http://www.plantgeek.net/plantguide_all_gallery.php )
-Alex