If you have the money i would go for a pressurised system for this tank, with DIY on a tank this size you may struggle.
Basically you need a CO2 cylinder to start with, a 5lb cylinder would be a good size (think about knee height)and should last about a year give or take, you can get bigger cylinders like a 10lb but they are quite large and you mightnt want something that size beside the tank, but whatever you get the best deal on at the time, personally i would look for a 5lb cylinder.
A cylinder will cost you about $80 and refills vary in price usually around the $25 mark, look up local welding supply shops and they should be able to help you out, if you buy a cylinder privately make sure it has its hydro test in date, every 2 years the cylinder must be tested for safety reasons, if the test is not in date this will cost you about $25 but it should be reflected in the origional price of the cylinder. If you purchase the cylinder from a store this shouldnt be an issue.
Then you need a regulator and a needle valve, any of the major online aquatic supply stores on the internet will supply these, these will cost in the region of $80, so if you shop around you should get a pressurised system for about $150, you will also need some co2 airline hosing but this wont cost much.
Good brands in regulators to look for are Milwaukee, JBJ, Aqua Madic these are all well known brands in the US, these brands will usually come supplied with a solenoid also which gives you the ability to switch the co2 system off at night time, you can operate the system on a timer so that it comes on and off by itself and will also save on co2 gas as it wont be running 24/7.
The needle valve is built into the regulator, the needle valve gives you the very fine control over the flow of the co2 into the tank.
You can also buy a ph controller but these are optional, if you have a ph and kh testkit you can work out the amount of co2 going into the tank, the usual target is 30ppm.
Heres afew links for you to look at
Measuring co2
co2
You should check both of these sites further if you are only starting into planted tanks but both have very sound info on CO2 and should get you started.
