I enjoy keeping a garden full of vegetables every summer. I could spend loads of money and use thousands of gallons of water every year, but I don't. Instead, I made a rain barrel out of some old materials I had laying around. I haven't turned on our faucet outside in years. I use the rain water to water my garden and also for houseplants and other odd jobs that I need water for.
Here are a couple videos that may help you plan a rain barrel for your home.
Tip: I recommend substituting flexible rubber tubing for the PVC. It's not as bad as PVC for the environment.