I think most of us know what giant scam diamonds are at this point, sometime you play the game to bring joy to the ones you love though.
I had very good luck with james allen when I got married several years ago. You can pick your diamonds and settings or go with a ready to order jewely. Much cheaper comparatively than a local store. If you are one that is good/aggresive at negotiating I think you could do well at a high end pawnshop. We shop at costco often and I always look at the jewelry section when I walk by. They often have good deals on nice looking jewelry but the selection is quite varied. They might only have have a 20k set of earnings in stock when you are looking to spend 1/10th of that for example. They are VERY good at returns if you order via the internet though
https://www.jamesallen.com/matching-pairs/?CaratFrom=0.05&CaratTo=10&PriceFrom=2000&PriceTo=5000&ViewsOptions=Images&ps=10