Make sure you seal your foam before you paint-- the foam will just suck up the colour and not get that nice glossy, metallic sheen otherwise.
As for the jewels, you might want to look into resin casting tutorials. It's a bit of an involved and slightly expensive process, but then you can make any shape of jewel in whatever colour you want!
DeviantART // Tumblr // Facebook // Instagram // YouTube
- Judal (Magi: Labyrinth of Magic): 16% (Wig Overhaul) Katsucon 2017
- Galaxy Print Shiro (Voltron, Original Design): 70% (Arm Work) Katsucon 2017
- Blanche (Pokemon GO): 82% (Sewing) Katsucon 2017
- Lelouch [Emperor Robes] (Code Geass) : 4% (Patterning) 2017