What do I need besides the Vigorous Herb to make any of the jewelry?

You need a Pegasus. They come in several colors. Each color Pegasus makes a different color crystal. The crystals are used in the jewelry machine.

Pegasi (this is the correct plural of Pegasus. I looked it up) are usually obtained as a prize for a holiday mission or some other special event. They are not currently being offered for sale in the market. (as of 3-24-13)

You'll need one of the following animals. Listed are the animal, the gem it makes, and it's jewel machine product. And of course, you'll need vigorous herb to feed the animals. This list is complete as of August 11, 2014.
-barbie pony: candy diamond --> candy diamond crown
-black pegasus: black diamond --> Halloween earring
-Christmas pegasus: cat's eye --> cat's eye brooch
-crystal pegacorn: purple crystal --> purple crystal necklace
-golden pegasus: gold --> gold bracelet
-lace heart unicorn: pink heart diamond --> pink heart diamond ring
-mother and baby pegasus: opal teardrop --> opal teardrop necklace
-nightmare: fire stone --> fire charm
-ocean blue pegasus: aquamarine --> aquamarine necklace
-pearl pegasus: pearl --> pearl necklace
-sapphire pegacorn: sapphire --> sapphire ring
-sugar plum fairy: amethyst gemstone --> amethyst pendant
-rainbow unicorn: rainbow diamond --> rainbow diamond ring
-wicked unicorn: moonstone --> moonstone ring