The first thing I would do is get rid of the incandecent bulb. They produce lots of heat, not much light & use lots of energy. Replace it with one of those 'energy saver' type bulbs. They produce much more light, much less heat & also use less energy. The next thing I would do is replace teh 50/50 flouro tube. Flouro tubes come with different Kelvin (k) ratings. The k rating refers to the colour of light that the tube emmits. Look for a tube with a k rating between 6,500 & 10,000. Tubes in that range are a good compromise for plant growth while still being pleasant to look at. Here's a link to heaps of lighting articles that you may fisnd worth having a read of:
http://www.liveaquaria.com/general/g...al_pagesid=308
I wouldn't worry about co2 for the time being. You don't really need it & I think it would just over complicate things for you at this point. It can be a little tricky for a beginer with a small tank. Leave that until you have a bit more experience.
Your fish should produce enough waste to get the plants going for a little while. You may need to add a liquid fertilizer after the plants are established & starting to grow but it is likely that they will get enough nutrients from the fish waste to keep them healthy for a long time. If you do end up needing a fertiliser, I recommend the Seachem Flourish range. You would only need to get the Flourish Comprehensive. No other additives would be needed. Only get a fertilizer if your plants start to show signs of deficiences such as brown spots or patches on the leaves or yellowing of the viens of the leaves.
Having an airstone on the tank is fine with plants when you are not using co2 on the tank.