Drip irrigation is a form of watering which can be implemented in gardens for a relatively low price tag while keeping water usage and waste to a minimum.
The simplest and cheapest form of drip-irrigation I’ve found is probably the bucket drip. Buckets can be found for free from local businesses and fast-food restaurants, while tubing, drip-controls and connectors can be found at local hardware stores for reasonable prices.
Larger reservoirs can also be used in a similar way.
Drip-irrigation supplies necessary water to plants without wasting precious water resources through overwatering and subsequent evaporation and runoff.