the proportions really depend on your preference/palate, but you can compare some of these to get a sense of what works for you:
I do a steak rub with coffee, my own mix. I grind the coffee extra, extra finely add s & p, onion & garlic powder. Might add the paprika now too but not the sugar or coriander.
Our son and his buddies did the just coffee thing whilst camping, but we found chewing the grounds a little of a pain.