I have a cistern, a 250gal. tank from TSC. I mounted it on a 40"high platform and collect from one side only of my shed. it stays full most all the time. It has a 1" outlet, so even gravity fed it can put out good flow. I use it for equipment washing, as it is my only water source, using a gas pump, of course. If I wanted to be mobile, I would still collect it this way and probably buy a smaller tank (about 100 gal) and pump from one to the other in a truck bed. THis way you could not have to disturb the "plumbing" I have a commercially available self cleaning screen mounted on the downspout to flush out leaves and debris. You can find these on many rain collecting websites. They are pretty cheap. I also would consider one of the 200 gal "totes" that I see for sale often, the ones with the metal cage. They sell around here for $50. Collecting water is really easy, if you have a roof. Gutters are cheap also.