Well the cheapest way is the DIY method of useing soda bottles sugar and yeast, the nutrafin ladders are very effective if thats what you mean, i use those myself, but if you are to go the diy method you need a Ph and a Kh test kit in order to be able to measure how much co2 you are adding to the water and there is no other way around this, you would have to buy those also, if you overdo your mix you will hurt or possibly kill your fish, so you have to be able to measure how much co2 you are adding to the water.
But if you mean the nutrafin ladder yes they are very good, and sugar and yeast are cheap.
