CO2 IS WORTH IT.
YOU CAN SEE A 1/3 INCREASE
You can use a slew of methods, from the 5$ pucks, to the 150$ boost bucket, to a tank and regulator to a CO2 generator. All of them work.
If you have a small area, use pucks or buckets. If you have a medium to large area the tanks work great. If you have a huge area, use the generator.
You get more, better tasting, fuller buds! No way to argue it, it is a fact, CO2 is air for your plants. Only use during the light cycle. Keep exausting to a minimum while using, other wise you will not get the ppm you want.
Chears!