Start with a formed or padded clothes hanger. You will want one where the hook at the top will turn different directions so it can be hung in various ways.
You will also need a turtleneck shirt -- black is good but any color that will show off your jewelry pieces the will do. Hang your turtleneck shirt onto the hanger and stretch an elastic hair tie around the waist area.
Thread a medium-size safety pin horizontally to the inside of the shirt on one side near the top.
(inside of shirt)
(outside of shirt)
This pin is to hang your earrings:
Stuff the top part of your shirt with bunched up tissue paper or bubble wrap. You don't need that much but just enough to give it "body" (pun intended) and the shirt isn't totally "flat" ---
Take another safety pin and tack the back of the neck part of the shirt so it closes tighter and this will cause it to stand up straighter. If your hanger is padded, you can pin the collar to it.
Take one of the sleeves and tuck it into the elastic at the waist. This sleeve can be used for hanging a bracelet or two.
Your mannequin display is now finished and ready to hang anywhere you wish.
You can even make a similar one for men's jewelry such as this shirt for showing off a tie tac.
Hang these in such a way so people can walk directly to them -- they will want to get a closer look. If you have anything to hang them on, try using a coat rack as a free standing display.