Have you looked up Newman's shrimp bowls on this forum? Do a search, his specs will give you an idea of how to get started. Basically, you lay down some wet dirt and cap it with sand, most of the time. The point of using soil is to add nutrients for your plants to use, so you don't need root tabs if going that route. You do need root tabs if you use only inert sand.
Good for your for getting a master water test kit!
No need for salt or those other additives. You may want some Seachem Flourish to fertilize the bowl and get the plants going. That stuff is great to hand on hand for any future tanks you might set up.
Low light plants that are small include anubias petite and various crypts such as crypt parva or even crypt wendtii. Dwarf sag is very cheap and very pretty. Java fern is another option, which can be attached to rock or wood with string. Moss such as christmas moss would look nice. Subwassertang is also nice! You have a lot of options. What kind of look are you going for?
Well, before you answer that, take a look at Newman's works of art. They are just awesome.