Congrats on the enormous peak :0
Since Rapid Spinning is Starmie's main mission, I suggest going with Surf / Hydro Pump and Thunder
. After Rain Dance, Surf and Thunder have no problems scoring an OHKO on Gengar and a 2HKO on Jellicent; Tyranitar also has a good chance of being one-shotted in the Rain. Hydro Pump provides you a more definite chance in scoring an OHKO on TTar / Sableye / Scizor (it also 2HKOs TTar in Sand) in the rain.
You may also want to try the currently popular Bulk Up Breloom
for some bulk that can dismantle non-Specs Rotom-W / Scizor / Landorus volt-turn combo. Drain Punch + Poison Heal keeps Breloom alive. Since you have Scizor for the strong priority, I think you can afford to make this change on Breloom.
Breloom @ Toxic Orb | Poison Heal
Careful | 236 HP / 212 SpD / 60 Spe
Drain Punch | Seed Bomb | Spore | Bulk Up
EDIT: Another option is giving Breloom Stone Edge or Facade
, so that it's not set-up bait for Dragons and Volcarona, over Swords Dance or Mach Punch on your SD Breloom.