Co2, please help! X(

Not sure why anyone would find pressurized CO2 all that confusing or even expensive. I was more daunted with the requirements of setting up and operating a DIY system.
What you'll need are;
- a tank - they cost about $100 new give or take depending on size, you might find a used one for less or even the refill place may rent you one for very little
- a regulator - they can vary in price a lot depending on make and type but around $100 to $150 will buy you a decent single stage one
- a bubble counter - may be included with the reg but otherwise they're cheap at $10 or less
- a check valve - may also come with the bubble counter but again cheap at $10 or less depending on quality
- tubing - you can buy CO2 proof tubing or use plain air tubing, the CO2 tubing is a little more expensive at about $15 for 5 m's and has the advantage that it minimizes loss of CO2 but a lot of folks believe the loss is so minimal to not be worth it
- a diffuser or reactor - there are many types ranging from $10 to $50, personally I like the in-line diffuser on the canister or pump in-take pipe but everyone has their own opinion on it
- a drop checker - used to monitor the CO2 in the water, sells for anywhere from $5 to $50 but $10 should buy you a reasonable one that works fine
Setting it up is relatively straight forward, follow the reg's directions and ensure the main pressure valve is off before turning the gas on at the tank. Set the pressure at anywhere from 10 to 35 psi depending on the diffuser/reactor your using and then adjust the needle valve to give you 1 to 2 bubbles per second in the bubble counter and your off to the races.

My opinion is a wee bit different then Steves... But we all have our own

Not expensive? He just listed parts over $250 and didnt even mention them all or any cheaper option.. CO2 systems are often the most expensive parts of a planted tank (but dont have to be, see below). Also he forgot to add two critical pieces of equipment (for the type of setup he is describing). A needle valve and a solenoid to automate it.

Not confusing? Sure its not confusing once you have one and have used it and know whats going on, but buying 10 pieces equipment, making sure it will all jive and work properly can be just that, Confusing. Not to mention dealing with pressures that can be dangerous makes many of us hesitant.

Personally I went with a premium GLA system for my first setup and I couldnt be happier with the quality, the instructions, and support I received. Yes it was expensive, but teh support it comes with and the knowledge I learned was well worth it.

Look on the for sale forum, there is a lot of member selling paint ball setups for $40-60 and all you need is a $15-20 paint ball tank. this comes with everything to get started except a solenoid. this works great as a beginner setup. The GLA one you are referring to is nice as well and should also do a good job, plus comes with great support and information. Then later you can decide if you want some of the benefits that some of the nicer systems offer.

Hope an alternative opinion helps you figure it out

I feel a lot of the confusion comes from looking at the whole rather than looking at the parts and getting down what each does for us. When we understand the parts we can begin to look at what different levels of those parts can do for us.
The CO2 tank we can figure what it does. But it is an important decision.
The CO2 regulator--It has to fit the tank and it cuts the high pressure in the tank from 800-1000 PSI down to a level we can use better. (5-50PSI?)
Solenoid--It is a switch powered by electricity to open and close a valve (gate?)Lots of people use a timer to tell it when to open/close.
Needle valve--This lets you make fine adjustments to the CO2 flow. Used with adjusting the reg output, you can get it set just right for what you want.
How you tie these together is part of deciding which make, model and kind of parts you have chosen. Some use solid piping, some use flexible tubing.
Check valve-- A little item to keep the water from flowing back from where the CO2 meets the water. A good one will keep the water out but let the CO2 go through. Like a one-way gate? Trouble is that a good one is hard to find!
You will likely use tubing to go from this set of parts to something to mix the CO2 into the water. Diffuser, atomizer, reactor are all some common names for parts to do the same thing.
There are lots of options on each of these parts. The commercial setups that are often thought of as regs are really regs with many of the parts added already. That sounds like the simple way but the flaw is that those parts are often not really very good.
That is where many get around to picking and choosing what level of expense versus quality of parts fits best in their mind and situation.
I suggest a study of each part before deciding on which fits you .