Honestly you can do a lot of shit with Celesteela. Heavy Slam/Flash Cannon is your obligatory STAB, then you can use Air Slash for secondary STAB, but it's not necessary: Giga Drain/Seed Bomb takes care of Rotom-W, Gastrodon, Jellicent, etc., Fire Blast I feel will be mandatory to take care of Steel types, but you can also use Earthquake, depends on what you need to kill the most, Skarmory or Heatran. Both together work as well. Stone Edge takes care of Zapdos, Charizard-Y and a couple more which otherwise don't give much of a shit about you. But instead of thinking about all this you could just do a simple Leech Seed set to annoy the enemies you can't counter and just go more defensive.
