Adding mulch to your soil helps it to naturally retain moisture. Ensure the soil is moist before applying the mulch to it. Either use pre-bagged mulch from a garden centre, or grass clippings and dry leaves work well as a free alternative!
Plants that are native to your home country and environment will naturally require less watering and maintenance. Use the internet to help find plants which will be naturally suitable to your environment and will thrive the best on the minimum of care and water.