Route 9
Your best bet is cycling along the route till you hear the grass rustling. Step on that patch, and you have an 80% chance of encountering Audino, at level 31-34. Keep beating this Pokemon, preferably holding a Lucky Egg, and you'll be up a few levels in no time, becaise it gives out a huge amount of Exp.
Also try and use some Ice type TMs if you find any.
Source: played the game
Good luck and cheers! :D
