The crafting station is available in furniture stores. Go to the one in Wizard City's Shopping district and you should find one.
When it comes to recipes, the only jewels I bother to craft are the pet gems. Their recipes are sold by the Pet Shoppe Boys in the Pet Pavilion. You will get a random pet jewel for your school back - this is the way to get gems with your school's Giver, Dealer, Sniper, Striker, Assailant, etc.
As for other gems, crafted jewels will come back random in both level and type. The reagents are difficult to gather and then they often get wasted on a jewel that is the wrong type and wrong level. Crafting regular jewels is a much bigger gamble than the pet jewels. For most gems, you'll have better luck figuring out where it drops and then farming mobs to get the type and level you need.
But, don't let me discourage you too much from trying it out. Linked below is an excellent guide to jewel crafting, including a list of recipe locations organized by level, and all the ingredients that each recipe requires.