a necklace or similar item is not good or nice by virtue of its cost.take her to a craft fair and buy her something that will always remind her of YOU and the time you spent with her. maybe get it customized on the spot. try a leather belt.
It s hard to define good . Some people think $500 is good some say a few thousands. If you ask my opinion, you can get a decent one for a thousand, with some diamond and all.The risk is you don t know what you re buying. These pawn people are like car salesman. It would be wiser to buy from a reputation shop with guarantees or certificate.