We bought some regular trash cans once to use in a pinch, and lots of 5 gallon buckets, which are a nice size to use. When they are full, we can put the lid on and stack them up, and put out others to catch the new rainfall.
Our plan is to set up a swimming pool and collect runoff from the roof. Use mosquito dunks and cover the pool. We should be able to adjust the filter to back hose setting and pump water to the garden with some adjustments.
We’d really like a cistern, but that’s pretty expensive, so the pool is a good step for now. It’ll hold 4000 gallons.
My neighbor buried two 1500 gallon tanks in his yard when he built his compound. We live on solid limestone, so it took a lot of digging. Both have been full for the past couple of years. He is getting ready to install a pump for his garden and lawn.