Product photography is something that takes a while to learn. And I am still learning. I have found it difficult to consistently take nice quality photos of my gemstones. The most difficult part is getting the lighting right.
What I have found works best is taking photographs outside on a cloudy or overcast day. Of course, weather conditions do not always allow. If it is a sunny day and you can take them in the shade, that will work well too. You may still need to edit some to brighten or tweak the color, but with this technique, often times you do not need to edit at all. Those are the results I like best.
Using a small tripod can help with keeping your camera steady while you shoot, but if you have a steady hand, it is not necessary. And a micro lens or adjustment on your camera for close up shots is very helpful in getting clear, close detail.
Another method that I have tried was with using a table top studio with lights, camera stand, and a fold out "box" made of white fabric to diffuse the lights. I gave it a try for a while, then decided I didn't like it. I thought I might have more consistent results with my photo box and not have to do any editing. Well, that wasn't so, so then I decided to just work with diffused natural lighting in my studio.
Then I found this post on a blog named Handmadeology. I really like this article because it gives another technique that is fairly simple and does not cost a fortune. If your photos are not turning out as good as you would like them to, you might want to give this set up a try. The article is called "A $6 Dollar Solution to Photographing Jewelry."