I said archetype, which is like weather, heavy offense, stall, stuff like that.
Okay, Skarmory it is. Well, we know that Skarmory hates Fire and Electric special attacks, so something with strong special bulk and resistances to those attacks. might do nicely. Let's say Gastrodon, since it also makes a good Rain counter while Skarmory makes a good Sand counter (Excadrill is banned, but Landorus and Terrakion may still be trouble). Then you'd just try to find things that can cover any weaknesses you see there, and so on. Once you've got a full team, try visiting this link. It has an OU threatlist that you can use to see if your team is weak to anything in particular.