Hi!
It sounds like you have a well established network of advertising that is working well for you currently!
Instead of looking to increase traffic, why not look to reduce traffic (i.e adwords cost) and A/B test actual conversion on your pages. Try to get more sales from fewer visitors.
Perhaps your Adwords are too broad, meaning that you get less qualified visitors. What can you do, to convince the customer to make a buying decision, today?
For new advertising methods, you could always focus on advertising on sites that pre-qualify the need to purchase jewelry. e.g popular wedding sites, people searching for expensive holidays (honeymoons), gift guides.
Analyse your online customer base. Are they all individuals, some businesses? Make a point of speaking to them, how they found you (who your referrals are coming from) what they liked about you, what occasion are they buying for. Go the extra mile for them.
If you notice patterns in your sales cycle how can you use this information (i.e more sales at the beginning of the month after pay-day) Find new ways to make your previous customers become repeat customers.
It sounds like you are already reaching far and wide with your Amazon business and that it's paying off.
I think if you use the information and data that you have at your fingertips you can ensure that you are making the most of the traffic sources you already have.