This is one method to make polymer clay rings that don’t have seams to worry about (as you would with a strip of clay). If you have the insane variety of round cutters that some of us clayers do you could even get some decent sizing. The faux stone clays are a great idea for the rings. Any of the granite or even the clays with big, obvious glitter would work. Make several thin rings (as the tutorial has) or a single thicker piece.
The only part I would change is ensure you cure your clay at AT LEAST the package time and temperature. Rings get handled and played with and worn and for maximum durability you’ll want to cure your clay well.