i get everything from www.gregwatson.com
, but commerical products are available around you to save on shipping.
i always forget what the commerical names of some of the products are though. I just know that Espon Salt is MgSO4 and you can get it very cheap ($1-$2 maybe) at any pharmacy store like Walgreens, CVS, etc.
If you want to raise KH along with GH, then you need Calcium CARBONATE (CaCO3), not Calcium Chloride. You can get CaCO3 from Home Depot, but forgot what exactly they call it. It is on Rex's website somewhere I think. I think it is Pulverized Limestone. You can get a 20 year supply for like $10 with whatever it is
GH is the combination of Calcium and Magnesium in your water. That said, if you do choose to use Calcium Chloride instead to raise GH, then you can just continue using straight Baking Soda to increase KH with neither affecting eachother (GH vs KH that is). KH is increased by adding Carbonates (or Bi-Carbonates) to your water; hence the CO3 portion of CaCO3. Baking Soda is Na2CO3 (adds bi-carbonates).
I am not sure about the gravel size. As long as it is something that roots can grab onto then you shouldnt have a problem.
The primary problem with not fertilzing is that algae is going to love it. As long as you keep the lights on the tank and do water changes then the plants will at least sit there and probably not die for quite a while. Wont look good in any sense, and you wont see much, if any, growth.