My first inclination is to say don’t get one. But on reflection they can be useful for small pieces.
If you are doing jewellery scale work, you won’t have to worry about going to 3 layers. The reason for avoiding 3 layers on larger pieces, is that the kiln cools too quickly to anneal other than 6mm (t layers). Of course you can use 3 layers of thin glass and not exceed the thickness suggested.
The kiln will work with any fusible glass – S96, Bullseye, Uroboros, Artista, etc. Although you cannot mix them in one project.