The easiest way to obtain an Emolga is to just trade with that dude on route 7. It's easy to catsh a Roggenrola because it has the ability Sturdy. You can find the Roggenrola in the Wellspring Cave. If you want to level it up easier, just use one of your strongest pokemon to battle, giving the Roggenrola your Exp. Share(
this only works if you have the Exp. Share, of course XP).