Once while working 80 hour weeks and living in an apartment, I found it difficult to keep all my plants watered. I had accumulated too many plants and invariably, I would miss one and it would die. I designed this modified hydroponics method to give me a bit of wiggle-room when it came to watering the plants.
It requires little in the way of expense unless you count buying lots of family size jars of peanut butter to get the styrene containers. I also pressed into service anything I had that would hold a cottage cheese, yoghurt or butter tub. That included old florist vases, small fish bowls, candle bowls, the aforementioned peanut butter jars, mixed nut containers, 1 and 2 liter soda bottles with the tops cut off and the quart deli containers that contain coleslaw. For the larger pots, it was difficult to find large styrene containers so I often had to settle for translucent rather than transparent which is more desirable. This works best if you can easily observe the water levels. I found a few styrene gallon containers with treats in them from Costco or Sam's Club. Otherwise I pressed into service, vinegar jugs with the tops cut off. Once I even cut off one of those huge 5 gallon jugs that offices have delivered for drinking water to accommodate a quite large size pot.
The square pots presented a problem for a while until I found square bottles of fruit juices and fancy expensive mineral water. I posted a sign at work asking for these and got some donations. As you can see from the photos, I use salsa glass jars, styrene mayo jars (cut off), anything that will accommodate a small pot. The drink containers used in most fast food places have smaller bottoms so they will fit in your car's cup holder. These are great for rooting plants because the smaller bottom makes it easy to find a water reservoir to fit and these very tall cups are good for rooting trees and perennials with a tap root.
Containers are relatively easy to find and the only other thing you need is a wick. I use strips of panty hose just like the ones I use to tie plants to a stake. You can either place the wick in the pot before you add the soil/plant or you can poke the wick up into the soil from the bottom using a small stick, pencil or screwdriver. It is helpful to wet the wick with water before placing it as it sometimes takes a while to get wet otherwise. You will need enough wick length to provide about 2" inside the pot and enough left over to reach the bottom of the water reservoir. Thick nylon cord can also be used but whatever is used for wick must be impervious to rot. Cotton wicks only last about 6 months. Also if your wick is too thin, the plant won't get enough water. And, for a huge pot with a large plant, I have used the whole leg of a panty hose as the wick.
When filling the reservoir with water, keep the level at least a half inch below the bottom of the pot. Otherwise you will have a plant sitting in water which will drown the roots. Then, as long as there is water in the reservoir the plant will be fine. If you like your reservoir of water nice and clear, don't ever water the plant from the top or the nutrients from the potting soil will wash into the reservoir and will grow algae. It is easy to clean but some might not like the color of brown or green water. You can see this difference in my photos. Always begin with a well watered plant.
I have also constructed a self-watering mechanism for a hanging basket using the panty hose wick. I saved the huge black plastic salad bowls from the deli that were used at work for parties and lunches. I planted in the largest one and then stacked it in a smaller one to use as the reservoir. I used a whole panty hose leg for this as it was quite large. It is of course not transparent but can be used like any self-watering pot. I re-purposed an old wire basket of the type used with coir lining as the container and hanger for the whole thing. I have also used the tall round plastic kitchen garbage cans as a reservoir. (Spray paint with plastic paint the color you like). A hanging basket will fit one quite nicely and again a whole panty hose leg makes a suitable wick. I have 4 that I have been using outdoors for 10 years with no problems except one must check and adjust the water level if it rains.
The only thing I've not addressed is getting a drainage hole for the "pots". For butter tubs, fast food drink cups etc., I use a wire fork heated on my range to melt the holes. When planning to use a wick, be sure to make the hole large enough such that the wick is not compressed or constricted. The water is delivered by capillary action and if the hole is too tight on the wick, it slows or stops the wicking action.
This technique can save your plants and like most "self-watering" methods produces a constant supply of moisture to cuttings, seedlings and seeds or to your prized house plants you would not want to lose.