This is a difficult question to answer because we don't know what size cylinders you are going to use, and how much you are planning on using them. If you only plan on actuating the cylinder once, then you need to figure out how much volume of air is required to fill the cylinder at 60PSI and you can calculate the volume of the storage cylinder. Some small amount of calculations later you can find out how many storage cylinders you need. Now the rules state that you can only have 4 storage tanks (identical to the 2 supplied in the kit of parts) - refer to The Robot section, <R84>.
If you need more air, then it is time to start thinking about including the compressor on your robot. Then you might be able to reduce the amount of storage cylinders you have depending on how often you want to use your cylinders during a match.
Hope this helped!
