I don't much care for undergravel filters, but if all you have is an air pump, it's pretty much either that or a sponge filter. (I'd recommend the sponge filter)
As to the undergravel filter, you really can't use anything but gravel/coarse sand. Anything finer will form a nearly impermeable layer, preventing water from flowing through (and rendering the UGF useless in the process)
If you are set on using a UGF, you might want to look at one of the calcined-clay type substrates (ones like flourite) since they are gravel-like in grain size. If you want something cheap, some sort of kitty-litter, or oil absorbent. I don't know what you have available over there, you may have to test a bit to find something that works well.
Another method that can work with a gravel substrate is to get some of those pots made of compressed peat fibers (see pic). put a mix of soil/sand/clay/whatever in the pot, plant the plant rootball in the pot, and then bury the whole thing in the gravel. It will provide a pocket of high nutrient, high CEC substrate right near the plants roots, but keep it contained so it doesn't muck up the tank, and you can still use an UGF.
As to the light, the cheapest/easiest would probably be to just install a couple incandescent sockets, and then put in some daylight spectrum compact flourescents.