The point of the regency period clothing was that everything was simple and elegant. Take a look at my Regency Clothing Page to see examples. This meant the jewelry was also simple, to match the same theme.
Regency Period and Jane Austen
In the A&E Pride & Prejudice, Elizabeth wears a simple cross from pretty much every scene. Sometimes the other girls wear a simple strand of pearls, or no necklace at all. The aim is for simplicity, the natural beauty of the woman.
You can see Charlotte (on the right) wears simple earrings, but the other girls wear none at all.
Here's another scene with Charlotte, with a different necklace and earrings -
Again, very simple designs, meant to be subtle highlights. They would NOT wear gigantic jewels or big, ostentatious designs. This was considered to be in very poor taste at this time.
Honestly, I have done a ton of searching of regency era portraits of women and pretty much NONE of them wear earrings, necklaces or other jewelry. They are reflecting their natural beauty with the simplest of white dresses and nothing else. At most they have pearls or ribbons in their hair as a decoration, which is pretty much always worn up.
Mrs. Clay in Persuasion from Masterpiece Theater 2008.
Jane Austen herself wore a topaz cross, given to her by her brother. In one of her novels she has a character receive an amber cross. Small, dainty crosses were very popular during this time period.
Note when you search on the web that there was a COMPANY named Regency that made big, gawdy rhinestone designs in the 1950s. This is NOT REGENCY ERA JEWELRY :)
Regency Rings - simple in design
Regency Necklaces - crosses, pearls
Regency Earrings - wire, not posts
Regency Period Information