It is hell of a job to do good picture
I sell sometimes coin on ebay also I am posting pictures in my registry and take a good picture is a hard job.
First: Natural light is very good sometimes I go outside and block the direct sun with white piece of paper. If is overcast the picture seems darker, but too much light is not good
I used many types of digital cameras and they are the key. I would not recommend lower brand of digital camera and also make sure it has a picture stabilizer this make a very big difference in macro mode.
Also background is important there is always better picture with black background then white. (this is bad for NGC slabs PCGS has see thru)
My final word is not to overdue in lights and try diferent distances on macro then cut out the main coin in PH software
I always fill the memory card :-)