I don't think showing Gems and this kind of surprise gift is that good, but well.
I chose a pokemon among the best team helpers, with a good firepower. Basically a pokemon that is predictable, but still, really hard to counter.
120 HP / 172 SpA / 216 Spe
- Hydro Pump
- Ice Beam
- Rapid Spin
This version of Starmie can survive a CB Ttar Pursuit, has a good chance to 0HKO versions with low HP/SpD (when they invest in Speed for Jellicent for instance) and 2HKO anyway. This means, that it leaves a free room to a sweeper because CB Pursuiters are easy set-up fodders. It's almost a pokemon you don't want to counter.
There isn't much an enemy can do against this pokemon, anyway you can still spin. Countering this pokemon would mean having a Pursuiter (and there is no Pursuiter that can really kill a Starmie easily), or a Spin Blocker. Anyway, if Starmie can't spin, the star can still be a huge threat to almost anything with the coverage and the decent SpA.