The theory behind a drip feeder is simple: rather than depending on the water to trickle down through the soil, a drip feeder delivers the water straight to the plant's roots. It encourages a healthy root structure and deters fungus from growing on the plant's roots.
But save your money; there's no reason to invest in an expensive drip feeder watering system. You can DIY a perfectly good drip feeder just by upcycling what you'd likely just be throwing away.
A plastic water or soda bottle
Metal skewers or an awl
A length of old pantyhose
Just punch several holes in the water bottle; add more holes for dryer soil. Then, wrap the pantyhose around the bottle to keep dirt from filling the holes. Bury the bottle next to your plants with the mouth of the bottle above ground and you've got yourself your very own drip feeder.
Credit: The Gardening Cook