Hi adamcsoki,
Wow, we are so excited for you! With market research done (on pricing and competition) I think you have taken the necessary steps in doing it right, the first time. :) The only issues I can think of in line with reselling jewelries is on the type – genuine gold/diamonds/gemstones and brand name jewelries VS. the costume /handmade accessories type. With gold and gemstones you will need to have proofs that they are not fakes, and expect a costly Custom duty/taxes when you import, considering the prices of these commodities. Other than that, selling jewelries is surely a lucrative business. :)
A good tip I can think of once you offer these products, is to sell on the ideas. Give a story on what makes a piece special, and unique. Try to go beyond the typical product description everybody gives and find ways to stand out from the crowd. :)
Alice has listed more tips on selling jewelry for maximum profit, have a read from the blog Link hidden: Login to view
Keep us updated. :)