Are you talking water or soiless mediums?
What I really want to do is come up with some low cost options for everything but the medium for now. We will save the soils or coco peat soiless mixes for last because I want to focus on pH meters lights, growing enclosures etc. I’d also like to consider recycle/ resuse.
I think I also want to have options. For example for testing pH like the $15 meter and the ph up & down and then the ph drop testing kit would be the second option and the third option would include natural pH adjusters.