Shooting macro is the key to photographing details.
A lens that is not macro will not allow you to get close enough to photograph sharp details. Purchasing a macro lens will not limit you to only up-close photos of miscellaneous images. Many macro lenses can also be great for portrait work.
I shoot with a 105mm 2.8 and use it for rings and outdoor art but I also can quickly turn and use it for portrait work as well. Very versatile.
The tip to photographing detail images is to get close and also use manual focus if possible. I find it hard to use autofocus for small items so switching over to manual focus is my key to a sharp image. However, remember to rest your elbow on your hip or something near you to steady your hand.
For ring shots a flash may be necessary to bring details out in the diamonds. Generally I will bounce the light rather than directly point it at the ring. My favorite macro lens is the 105mm 2.8
Actions can also bring out the details of the ring that you may not have achieved in camera.
The photo above was edited with Make Jewelry Sparkle - Photoshop Action and we ran the Colorvale® Gems over the diamond to bring out the details.