​How Can I improve my Sales.

I have made a website (sagems.co), which sells lab grown diamonds. I am currently competing against biggest names in USA could be Brilliant Earth, Bule Nile Etc. I am competing in terms of pricing of Certified Lab Grown diamonds, currently I can say I am cheapest B2C supplier of Certified diamonds.

I would really appreciate if someone can go over the website and tell me how can I use my competing strategy to the most so that I get more business. I currently have sold 3 stones but I spend a lot on Facebook & Insta ads. How can I improve my marketing to show people real savings on diamonds which marketed and sold at very high markups!!