For most collectors, a common 5X or 10X jeweler's loupe is sufficient for finding varieties and errors. They are compact enough to carry in your pocket where it's always handy. They can be purchased for around $5.00 - $10.00.
The same magnification is available in hands free versions, which work well for taking pictures when accompanied by a camera stand. Many collectors will fabricate their own camera stand out of household items, all it needs to do is hold the camera above the magnifyer.
In today's high tech world, some collectors prefer to use their computer screen. There are many USB microscope cameras available today from prices as low as $10.00 to over $1000.00. These cameras offer their own light source as well as being hands free.
If you don't mind spending more money and need professional photos, a trinocular microscope allows for stereo viewing with a third hole for a camera. USB cameras are available that fit the eyepiece tube, or adapters are available to allow for a hand held camera to fit.