Usually I get the aquarium salt in 1/2 gallon cardboard milk containers from the fish store. That lasts for a few years in my smaller 30-gal aquariums, but instructions are on the side. Something like a tablespoon per gallon, but it depends on the fish. Example: guppies can take more and prefer more. You may be able to source larger quantities on-line for reasonable prices.
The Calcium Carbonate I got in a 5lb container for marine use. I am sure you can find it much cheaper than I paid for it. The advantage is it is purified so it wont cloud the water with impurities. I haven't used it in a long time since my tap water already is well buffered.
I use the paper strips for PH, since it is cheap, quick, and they store well. The same is true with alkalinity. You can purchase a big honking box of 100 or more online for cheap, though lately the pool stores have been a good supply simply out of convenience. I figure the accuracy is more than enough for fish.
BTW most of my fish die from old age. Rarely from introduction, disease, or water quality. Just lost my first fish in more than a few months from getting stuck in a decoration yesterday, I couldn't get it out. Its out now, but got a swirly.
My big problem right now is my tetras are breeding, and starting to overcrowd. I have a lot of plants and cover, so many make it to adulthood. They are Emperor Tetras, not the fragile little Neons. I had to stop raising angelfish for the same reason.
I used to be a big discus guy, I love those fish! But when I moved to the house I live in now, my transfer was a disaster. The power company turned off the power before we moved in, but the fish were already there. It was winter, and they don't take kindly to being chilled. So mad! Expensive loss, so I never started back up.
