Depending on your environment, that is, the context where you are living and gardening, you may be able to collect rain water. Obtain rain barrels, as cheaply as you can, by searching "high and low" within your community for sources of 55 gallon barrels that are suitable for recycling. Be careful not to obtain barrels that are contaminated with deadly or harmful chemicals. Some barrels may have been used to store and transport carcinogens, or other life threatening substances.
Set up a system so that you can collect rain water from the roof of your house, or apartment, or condo, or whatever. You will be able to find great sources on the internet on setting up your water collection system. In addition to the rain barrels you will need pipes, buckets, valves and other items, depending on what you want to do. You can make your system very simple, or more complex, depending on your talents for conducting a mechanical project. This is a simple project. I am sure that you will do well with bringing it on line to meet your needs.
Once you have collected the water, you have to decide how you will apply the water to your yard and garden. Once again, the many, reliable sources on the web will help you to achieve success. Take care. Regards, Dr. Haddox