Put Sparky behind a tank (Goblin Giant, Giant); while the tank takes damage, Sparky charges and clears the defense in one shot. She's also very effective on defense against big ground pushes. Your opponent's Zap or Electro Wizard will reset her charge.
Tips
Send Sparky when your opponent's stun cards (Zap, Electro Wizard, Electro Spirit) are out of cycle.
Goblin Giant and Sparky is a classic, powerful combination.
Don't lead with Sparky alone; she's slow and needs protection.