The jewelry you purchase to sale to customers is considered Inventory. You should enter the cost as the amount you actually pay for the jewelry plus any tax or shipping. You can enter this information under "Inventory/Cost of Goods Sold". If you use some of the product for yourself personally, you will need to indicate the cost of the items withdrawn for personal use.
If any of the Jewelry is purchased for display or other purposes (not to be sold to a customer) you can report the cost of this jewelry as supplies.