Depending upon your body type, certain jewelry looks better than others and accentuates your good points. I know you know that already!
To look thinner, I recommend long chain style necklaces with dangling pendants. Do not wear a necklace where the bottom rests on the boobs. It needs to be a little shorter than that or you’ll look as wide as a battleship in your side view.
Symmetrical pins, worn alone on a coat collar or lapel or used to anchor a scarf, are an excellent look.
For earrings, long chandelier style earrings are a good look. Hoops look good on everyone. I’d avoid round, button style earrings. They tend to widen the look of the face.
Stacked bangles in a variety of patterns and colors draw attention to the wrists and can hide a thick wrist. I’d avoid tight cuffs. I also wouldn’t waste my time with a delicate bracelet, like a tennis style bracelet. If I’m going to wear a tennis style bracelet, I try to wear several constrasting looks. 
When I wear rings, I tend to go for the larger stones. I want to draw attention to my hands.
I’d avoid anything tight, tight choker necklaces, tight bracelets, tight rings, cuff bracelets, tiny pins, button style earrings.