I started off with mostly dry potting soil, so a lot of water was used initially from the container before an appropriate moisture level of the soil was reached before it established a good equilibrium. (I have also read somewhere that it is recommended that you water your plant and wet the wick first to prevent the initial large water use when using the "wicking" method and to start the capillary action).

Please take into consideration the size of the plant and pot to determine the appropriate amount of
water and size of bottle needed.  I was able to get 5 days of watering when the bottle reached a little less than 1/2 of its holding capacity (1.89 L bottle)

I have now tweaked my initial design a bit, in an effort to make it less clunky looking. Changed the look of the nozzle end for the wick and the overall width of the device. I added a cap, in case you want to close the top off (but, I don't recommend closing the top off completely in case you need a vent for the air to replace the water used).

I have also included a few different sizes and types of container/ bottle adapters and an extension tube. You might want to tweak the adapters if it does not fit your container. I have attached my 3d ipt files.

Additional materials needed:
1. A long wick made from an absorbent material like cotton which, should be the length from the soil (I'd say about 4 cm or more deep into the soil if you want) through the tube of the plant waterer into the container holding the water (touching its base).
2. A
water container such as a large bottle or similar with a neck (for attaching the auto plant waterer).
3. and of course water!

Previous working test design: https://www.youmagine.com/designs/diy-auto-plant-waterer