Hi Kiana,
OK, here's my two-penneth.
If you are selling any product online you need to in some way differentiate yourself from the competition. As some have said already, your products could be available elsewhere on other sites. This is common and it doesn't matter as long as you have a strategy against this.
Take a look at jewelers selling high-end watches. They all have the same watches but they tend to differentiate on service, experience and expertise. This is what you need to do but put 'you' as the centre of the brand.
You need to be all over the site to demonstrate expertise, create inspiration for your customers and really be the face of your business. This means creating an engaging blog, Facebook live content, Youtube content and really help people to find the right jewelry for the right occasion.
People buy from people. If you can get that right then it's likely you can make a success of it.
Regarding your agency.....cough, cough....... what KPIs do they have? (i.e what targets have you given them to hit?) Or have you gone into this relationship blind?
In short, you need to give them a target to hit by a certain date or else you are pulling the plug. And don't wait until that date to turn the screw. These guys are happily taking your money so you need to put the pressure on from day 1 and understand exactly what they are doing. Don't be afraid to get shirty because agencies have it too easy. Just remember how hard you worked to earn your money.
It's also important that you learn from this partnership rather than just let them get on with it. Because, if it doesn't work out, then at least you know for next time and you have the knowledge to carry on doing it yourself.
Learning on the job is all part of this process. I know you want to sell jewelry as your main job but you still need to learn how to run your business, market your products and generate sales. If you always rely on someone else then you will just hemorrhage cash.
Getting back to the agency question, here is some advice that should help you:
Set a customer acquisition cost - This is the amount of money you are willing to spend to get a customer. This usually depends on the cost of the product. Ideally, you want it to be a proportion of the profit you make on each item. However, if your products are low-cost, you will need to decide on a cost you feel comfortable with and then encourage repeat purchases further down the line where you will make the profit.
Set a clear marketing budget - Don't ever spend above your means. Be sensible and ask your agency to micro-test campaigns. Never through all your eggs into one basket with regards to keywords (on Adwords) or Ads (on Facebook). It should be a test, tweak, test, tweak mentality. If it doesn't work, stop and find another strategy. Your agency must demonstrate this approach.
Visitor Stats - Don't be fooled by visitor stats. A large number of visitors is pointless if they aren't buying anything. You need to find out where your 'target customer' (which you should know) hangs out online and go after them. You then need to give them reason to stay on your site, browse and then buy. Don't think just listing your products will be enough. They need content that engages them!
Collect Data - It's unlikely your sales conversion rate will be above 5%. That means, for every 100 people who visit, 95 are leaving without buying anything. If you don't collect an email address then you have wasted your time. Install an email capture pop-up and give people a reason to size up (maybe 10% off).
Build Relationships - Sometimes it is common for customers to need to interact with your business 7 or 8 times before they think about making a purchase. This means you need to capture an email address, engage with them and build a relationship. Using Mailchimp, you can set up a welcome series that can help you to warm people up before they buy from you. It takes a little setting up but it works.
SEO - Ask your agency what keywords they are targeting and why? Ask them what monthly search volumes each search term has? Ask them how they plan to help you reach the first page and if it will supported by any pay-per-click? Ask them what long-tail keyword terms they are targeting because these are the ones that will pay the bills.
Photography - I would invest in shooting your own photography. If you are using stock photos from the manufacturer then people will realise your products are available elsewhere. Try to put your own spin on the backgrounds and presentation.
Short-Term Sales Strategy - Everything your agency is doing in the short-term should be focused on sales. Yes, I know you need to build a brand but using social media is pointless unless they are working on driving traffic from ads. Facebook's organic research is now only 6% which means you are wasting your money if they are managing your social pages too. You need to pay the bills!
I hope some of that helps.
Matt
P.S Don't take any 5hit from your agency. Be tough with them and demand results.