DIY pH test for soil and water

Hi, this is my first time posting after lurking this forum for a while, I hope I'm posting in the right place.
I currently work on six acres in central FL which my family and I are hoping to dedicate to permaculture. Unfortunately, a large portion of the property is heavy clay or thick mud (especially summertime = nonstop rain). I recently had several soils from the property tested at a lab and most came back deficient of NPK and have very acidic pH, so our goal right now is to learn/try to amend some of these areas.
It makes sense to me that, for this process, we should invest in a DIY soil test for pH/NPK/nutrients but I am having a difficult time placing confidence in random ones I've found on Amazon or wherever, I guess because I'm not exactly sure what to look for. I have also considered getting a test for water pH just to be completely sure of the resources we are currently working with. If anybody has any thoughts on this or recommendations, I would be very appreciative to hear.

Also - any thoughts or methodology about soil amendment in general are greatly appreciated as well. I'm still learning. Thanks!

It looks like the UofF soil laboratory fees are quite low. I would probably send samples to them and skip buying a tester. You can test many samples before equaling the cost of the tester and buffer solutions, and you should be able to trust their calibrations/procedures. Also, you will probably test less frequently after amendments are added and areas get planted.

http://soilslab.ifas.ufl.edu/ESTL%20Home.asp

I sent samples both to my county extension and then to IFAS for more thorough testing. Altogether for only six areas it costed about $60. But the reason I want a DIY tester is to keep track of drastic changes while we are adding different materials to the soil, and so we don't have to go through a three week process of passing soil around the state just to make sure we are doing things correctly.
If everything you can get on the market is useless crap, then it will just be something we have to deal with. But that's the question, ultimately, if there are any testers out there that can be relied upon for some accuracy.

Soil Testing Kit Reviews is a good place to check out soil testing kits. The reviews are pretty spot on.

Hi, the above link does not work, but I am interested in doing my own soil test - PhD,  Phosphorus magnesium etc.  I am in New Zealand, but if it is available through ebay or Amazon the freight can be reasonable. I have three soil types although I only have 8 acres of sandy loom/.  Very poor ?acidic soil along a sand bank that is a few feet higher than the rest of the flat land.  More fertile lower soil. esp near trees.  Patches of pure buttercup where ground water flooding pooled for 4 months a year ago and I presume all the organic matter feed anaerobic bacteria and went acidic.  I don't want to pay for multiple tests.

Actually after writing the post, I found these online if anyone
else is looking:  https://homeandsoiltestkits.co.nz/collections/soil-diy-test-kits