I ordered my gems off this website called GemSelect, they have a good selection and it's easy to navigate. You can also have the gems professionally certified when you buy them, but they do provide certificates of their own.
Good experience with finding a variety of stones. Due to the vast selection, it is important to be able to search, and I had issues with the site not returning matches when I put in a specific size range. I was eventually able to narrow it down by sorting the items by size, but it was slower than if I could have typed it in. I also wish Gem Select would offer lab created stones (fully disclosed, of course!) so I could get some exotic colors more frequently. Overall, I love browsing and will continue to patronize, but this would put the site as my #1 go to.
I have been browsing stones on GemSelect for a few months. They have such a large selection and I found some stones I had never even hear of before visiting GemSelect! I cannot wait to receive my order and show my gems off!