a) low cost quality jewellery
b)Must be genuine gold, diamonds and gemstones.
a) and b) are generally mutually exclusive.
Bidz is a good place to pick things up, but be very careful about your valuations and don't fall in love with any particular piece -- almost anything you see on there will be featured repeatedly.
Remember to properly price the gold when you are gauging value. Many people neglect to figure in the differences between 10k, 14k, 18k, 22k and 24k gold when trying to figure out what a piece of gold jewelry is worth.
I actually have picked up a few pieces on Bidz before where the net price was barely more than the value of the gold itself (let alone craftsmanship, stones etc.) so it can be a good supplier -- just be highly discriminating in your bidding.