i don't think it makes sense to buy the coupons unless you're getting a reeeeallly good deal. (If you pay 20 bucks for a coupon that saves you 20 bucks, you really didn't save anything.) but honestly, I think the only reliable way to get facebook coupons is to wait for them to send them to you directly. if you've used facebook ads in the past but then stop, sometimes they'll send you a coupon to encourage you to come back.
mostly websites are fake and they will provide you the fake facebook advertising coupons. Please be sure you are on the right place and ask them for VCC with coupon they will charge extra but you should get and VCC with coupon.