I do custom gemstone inlays. If you search my posts they will turn up.
I use an Inland all in wonder lapidary unit. It is BY FAR the cheapest lapidary setup you can get. At least $1000 less than any other setup. That being said, it is meant for hobbyists, and has its limitations.
The unit is about $500.
I have come up with my own process of making the inlays, and I have good results. My inlays run from .020"-.080" thick, depending on if they are flat with the button top or they stick out.
I have never tried Opal, as it is too expensive for me to experiment with. I have cracked MANY inlays when doing my final passes, or when buffing up the stone. It is a pain in the butt sometimes. I built some tools to help reduce these issues, but there are some sets of buttons where I have had to make 6-8 inlays to get 3 usable ones.