Its not too difficult to get started.
The two basic techniques are to light the crystal from above or below. I chose to go with the latter. Here's an image of the rig I started out with back in 2008. If you read the description there's a writeup of my workflow.
Over the years I've tried tweaking things to improve things, the latest tweaks being a microscope base for ultra fine focus control, and a microscope objective for extreme closeups. But, some of my favourite images were shot with the original rig. A 50mm lens on a bellows, or extension tubes, will get you pretty close. Here's an image from back then using that rig.
The other technique is to light from above which give a totally different look to the crystal.
Don Komarechka is the master of that technique. Check out this video where he explains his method in great detail.
Hope that helps.
Fred.