We used eight-60 gallon water barrels. They were hidden from the eyes of any visitors. One set of five sat behind our garage and the other set of three were disguised underneath our sun porch and covered with lattice. Hoses were available to attach to the system, as well as the ability to simply place a watering can under the spigot. We had easy access to water wherever we needed it.
Our recycled barrels (of lemon-flavoring) were from a local brewery. It's important that the barrels come from a food-based source, since any chemical source would obviously be bad for the plants. Also remember that as rain water flows over a roof surface it can pick up pollutants such as bacteria from birds and other animals, and chemicals from roof materials. Consider these factors when using rain barrel water on edible plantings as opposed to flower gardens. For more information go to: https://www.epa.gov/soakuptherain/soak-rain-rain-barrels
Note: After we remodeled our garage to make it larger we lost the space needed for the rain barrels to sit. I posted this information in case anyone was considering water collection.