I'd suggest a white background with natural light for your listing photos. You may want to search "jewelry" on Etsy and see what pops up. There are simple tutorials online showing how to make a light box for Etsy photos. You may want to explore those. The simple white background and surroundings will help your jewelry "pop." There is also some free photo editing software available online such as pixlr.com that allows you to adjust the saturation, hue, brightness, lightness, etc. of your photos.
An example of what I think is a great listing photo:
https://www.etsy.com/listing/99140050/rose-quartz-necklace-rose-quartz-faceted?ref=sc_3&plkey=3afbdd...
