So you have no 3d modelling software, and no experience in modelling?

You really can't turn PSD files into props. At least, not easily and not well.

Your best bet, IMO, is to take jewelry someone else has modelled, and apply your designs to it as textures. For example, Trekkiegrrrl has a gold necklace with a square pendant. You can apply any design to the pendant, to change the look of the piece. (With transmaps, you can even change the shape of the pendant.)

Another possibility would be to do it with postwork, rather than trying to model it.