Today I received a few photography accessories in the mail, a set of Neewer Neutral Density filters, a Neewer Circular Polarizer, and a set of 3 grey cards. I haven't tried out the ND filters yet, but I pulled out the grey cards for my self-portrait tonight, accompanied by my new (thrifted) vest and new (thrifted) tweed blazer.
The point of grey cards is to help you easily set your white balance. I'll be honest, I wasn't totally thrilled with the result I got when I set the balance based on the grey card. When I set it based on the black card I got something I was happier with. This is my first time working with grey cards, so I'm sure I need to learn a bit more about how to use them.