Calling on the gurus: Running Facebook ads and ad copy

Lately, I’ve been running ads and doing A/B testing but I was wondering what are some of the biggest mistakes that you have noticed people usually make when running ads? Are they any books or blogs that you would recommend for ad copy?

I know we are focused mainly on automation and having MP run everything but I really want to improve my ads and was hoping you guys/gals could share your experiences and inputs.