I need to be careful with my PH. I don't want any chances of raising it.
I wouldn't worry about the pH. It is the KH that is more important, by far. The pH ia just a reaction to the KH.
Is there anyway to test the water coming out of your tap for the mineral composition? My well water is loaded with minerals and in layman speak is considered hard. I'm not running a water softener system.
Yes, you can measure the GH, knowing that most of the GH will be calcium. And, you can look up, or ask for your local water company water quality report, which usually lists the "stuff" that is in the water.
I was cringing over the price of lighting last week and now it appears the substrate might be more. Are there any *cheats*, as in okay, buy a bag of flourite for the actual areas you'll be putting the rooted plants in and then going with another material that's less pricey to fill the areas that won't be planted.
Most of us keep our tank as it is for a limited time, a year or two maybe, then we want to try something else. If you use different substrate materials in different parts of the tank, or layer the substrate, when you try to remove it for doing a good cleaning of the tank, you mix it all up. Even if you leave it in the tank, the substrate will mix up from the activities of the fish and the natural mixing of fine materials moving down, and large particles moving up. Plus, every time you pull out a plant you partially mix the substrate materials. I think there is a lot in favor of using just one material for a substrate, even if it is costly.
Inert substrates work fine, just not as good as nutrient loaded substrates. You can use Black Diamond blasting grit if you want a nice black substrate, and it is very cheap. Or you can use pool filter sand, which can have a color from white to black, depending on where you live. Then, use root fertilizer tabs to get nutrients into the substrate. Those are much better economical options than using different substrate materials in the tank, in my opinion.