Can you use black magic but not believe in god?

Just a clarification here, there isn't really such a thing as "black magic". Magic is power. It is the way the power is drawn and the manner in which it is used (determined by the practitioner and his/her ethics) that give the power its polarity. As to believing in god... which one(s). It is difficult to wield real power and not believe in something greater than yourself.

Conversely,

I completely agree with the clarification of black magick.

However, technically speaking, you dont have to believe in the array of Pagan Gods for your spell to work. You can just believe in the power of the Universe, (minus the Gods), and do what the CoS's (Church of Satan) do. CoS magick users believe in themselves, and believe that they get their own power through hard work and etc. They dont believe in any form of deity whatsoever.

In my opinion, though, magick should be practiced as a form of worship to the Gods. Magick is the highest forms of worship. And to me, who doesnt have a specific sect of Paganism I identify with, witchcraft is just as much as a dedicated religion as Wicca is.