If you're budget-restricted, your best bet is this Necklace. It's a great product, while not very costly. You can also check out this Nina Necklace. It's an item you're bound to love which also doesn't cost a fortune. You may also want to look at this Badgley Mischka Necklace. This item is not expensive either, but it will make a difference in your wardrobe.
For something in the middle of the price range, why not check out this Swarovski Necklace. While the price is very reasonable, this item is an easy wardrobe update.