Just to add some more thoughts to all of the good info Rex has given:
1) CO2 is CO2, if it comes out of a shiny or rusted metal bottle, or out of a blubbering plastic soda bottle. Both ways can supply CO2 for your plants. The real difference is in the startup cost (DIY probably even less than you mentioned), and the continuous maintenance. If you have the money, and don't see much joy in mixing sugar water yeast every two weeks, you will be better off with pressurized CO2. If you have very soft water (low kH) an automated controller will give you peace of mind and stability in your tank.
Also, for a tank with about 2 Watt/gal, you you will need less CO2 than say 4 Watt/gal, so DIY still is a viable option.
2) Robert from AB has mentioned a few good books in this thread https://www.plantedtank.net/forum/viewtopic.php?t=3956
. One way to start learning is to look at all the pictures at online vendors sites. This would give you at least a general understanding and the ability to differentiate between a sword and a vallisneria.
3) You might want to start out with one of them, and when the plant density has reached jungle character, add the second filter. I noticed that in my tank, in the beginning the XP3 was enough filtration and water movement, while now it is not sufficent anymore.
4) If those bulbs are two 40 (t12) or 32 (t8) watters (just guessing) and you have good reflectors this should allow you to grow a wide variety of plants. If you have a basic understanding of fluorescents and electricity, you could get another ballast and "overdrive" them which results in about 50% more light output.
Good luck with your tank...