Tee,
a good way to determine just how big of a rain barrel system you need is to look at your water bill over the winter months (this works if you do not have a green house) the less water used in winter will be the amount of the system size you would like to be close to . not to say you need a 2500 gal. system you cut that down by a 1/3 of the ratio.
my set up is about 175 gal.. however, i found myself in need of water in the dry spell so since i have the room to do so i want to go to a 300 gal system. but the garden is a 30 x 30 and there is seedlings and plants that all get watered from the rain barrels.
you can always find Large Caged square type containers. on line for sale just remember not the ones that have had harsh chemicals in them . most soaps are fine any of the cooking oils (Unused type) that have been in the tubes these can be cleaned with some effort and made usable for a rain system and not have so many containers to set up .
Sarge
