well magick is something anyone can do and doesn't require a deity. you're connecting with natural energy and focusing it in a direction to create subtle changes in your life. many spells call to certain deities, but that's in the writing, just omit them or change it to a different deity you believe in and it'll work the same. granted some spells work better for certain people than others depending on their likes. for example, all my spells have cinnamon int hem because i work best with that spice. some people might despise it, so they can't connect, therefore a spell that might work wonders for me, would fail for them. personalize everything to you.
Paganism is a very personal religion, not many people share the same beliefs, but generally speaking most people i talk to do believe in the threefold law to some degree, or basically 'you reap what you sew'. to what extent it's different for everyone. some people believe the universe will keep things in balance, others [like myself] feel sometimes you should take matters into your own hands. [please note i feel if someone did deserve a karmic slap and you chose to dish it out, you should take some time to reflect instead of instantly condemning them.]