The answer is, as much as you can. We live in the desert. Collecting water needs to be top of mind. Do yourself a favor, learn how to collect and utilize stored water for your daily needs. Tank N Barrel is here to help.
Some rely on wells, but a well is expensive to drill. There is the garden hose method or you can have water hauled in. These methods can be needed to supplement your water storage but, rain is free and so the gutter/roof method should be first priority.
Larger vertical tanks have enough head pressure to operate a garden hose. But, if you need to feed multiple places around the home or business you will want a pump and pressure tank combo system. The pump gets it there and the pressure tank keeps the pump from working over time. TNB carries all the pieces and parts necessary to get water from the tank to the home with adequate pressure.