I think it's kind of hard to have a set rule on what to grade. I think you should grade the cards by feel. If you really like the card and want to see it protected or if you think the card will get a gold label then you should do it. Kind of a silly approach, but that's what I do.
Currently collect: NON-SERIAL NUMBERED autos, Topps, and Topps Chrome cards of players in Bengals uniforms.