The key to good pictures is good lighting. The biggest and best softlight box available is an overcast sky or open shade, no direct sun. I have lots of lighting equipment, but no place to keep it set up. It is much easier and quicker for me to just do this outdoor setup.

The background is just a piece of white bed sheet. I wrap it around a large cardboard tube to prevent wrinkles when not in use. I tape it to the back window and have it fall with a gentle curve onto the table top. I open up +1 EV to get it brighter. I follow basic rules of composition:

1. When shooting a square or rectangular object, shoot it at an angle. A straight on shot is too flat; an angle shot is more dynamic.
2. When one looks at a picture, one usually looks at the top left and then across and down to the lower right hand corner. That is the way the elements in the picture should flow.
3. Vertical elements in the picture should be vertical, i.e. parallel to the side. Otherwise the picture will look crooked.
4. Get close enough to fill the frame with the item and still maintain good focus.

This film holder is another example of how a rectangular object can look much more dynamic when shot at an angle. Notice how the base of the holder (vertical) is parallel with the side of the picture. Otherwise, as I said before, the picture would look crooked or askew.

A white cardbord works well for the reflector. There may be reflections on the glass from the jewelry placed on it. The light from the bottom may eliminate that or you could place a piece of tissue paper on the glass. This setup would also throw light through a gem stone accentuating it better. The one thing you want to avoid are distractions such as hard shadows or a busy background.