Donald, gypsum only works with certain kinds of clay, kinds that most people don't have:
https://ag.arizona.edu/yavapai...
Amber, silt is a normal component of soil, which is made up of sand, silt and clay plus organic matter in various proportions. Soil texture relates to the proportions of sand, silt and clay in your soil. I wouldn't add grit to garden soil. If you add sand I don't think it would need topping up but it also won't do much good unless you add huge quantities of it in proportion to your native soil.
Yes adding 2-3" of compost every year or two is the way I would do it. If you're starting a new bed you could incorporate compost, otherwise topdressing it is the way to do it without disturbing the roots and it will work its way in as Larry said.
Which soil tests to get depend what you have already done and if you have a problem you want to solve. If you don't suspect an existing problem the regular test should be all you need. If you really want to test for nitrogen you could add the nitrate and ammonium test. Most of the time we just assume nitrogen is needed. That still doesn't tell you how much organic nitrogen may be in the soil that hasn't been converted yet, but for the most part that isn't available to the plants at the time of the test anyway.
You can test soil texture (proportion of sand, silt and clay) yourself. This article explains how:
http://www.ext.colostate.edu/m...
If you think you may have overfertilized then the electrical conductivity test might be relevant but otherwise I wouldn't bother.
I also wouldn't bother with the micronutrient tests (zinc, boron, Fe, Cu, Mn) unless you've seen symptoms of a deficiency such as interveinal chlorosis. If you have, often we can figure it out based on symptoms and soil pH. For micro problems a leaf analysis would be more helpful or, better yet, both soil and leaf. Usually micronutrients become less available to plants as the pH increases.
