When do you usually build armor/MR?
okay, so, I just played a cassiopeia mid game, and I was against an olaf mid. it made me think, "when should i start building armor?". Usually, My first items for cass are either Morell or Rabadons, then rylai's. When should I build my first armor item? should it be my first item? how many armor items should i build, cuz i usually like to go full ap