Walkthrough
Just east of Cerulean City is Route 9, which you will now have access to since you have the Chop Down Technique. Route 9 is a very long path that is full of loads of Wild Pokemon and Trainers looking to battle, eventually connecting and leading you straight into Route 10. You must reach Route 10 since that is where Rock Tunnel can be found.
Wild Pokemon
Grasses:
Rattata (20%): Levels 17-22
Spearow (20%): Levels 17-22
Nidoran F (15%): Levels 17-22
Nidoran M (15%): Levels 17-22
Raticate (10%): Levels 17-22
Fearow (10%): Levels 17-22
Nidorina (5%): Levels 17-22
Nidorino (5%): Levels 17-22
Grasses - Special Spawns:
Chansey: Levels 17-22
Sky:
Spearow (60%): Levels 3-56
Fearow (40%): Levels 3-56
Sky - Special Spawns:
Dragonite: Levels 3-56
Charizard: Levels 3-56
Articuno: Levels 3-56
Zapdos: Levels 3-56
Moltres: Levels 3-56
Trainers
Picnicker Alicia: Level 21 Eevee, Level 21 Gloom
Hiker Jeremy: Level 22 Onix
Bug Catcher Conner: Level 19 Paras
Hiker Alan: Level 22 Geodude, Level 22 Geodude, Level 22 Geodude
Camper Drew: Level 21 Sandshrew, Level 21 Raticate
Youngster Chris: Level 20 Diglett, Level 20 Fearow
Black Belt Brice: Level 23
Picnicker Caitlin: Level 21 Goldeen, Level 21 Pidgeotto
Obtainable Items
Great Balls: Defeat Picnicker Alicia
Poke Balls: Defeat Hiker Jeremy
Super Potion: Near Hiker Jeremy
Poke Balls: Defeat Bug Catcher Conner
Ether: Near Bug Catcher Conner
Poke Balls: Defeat Hiker Alan
Great Balls: Defeat Camper Drew
Super Potion: Near Camper Drew
Poke Balls: Near Youngster Chris
Poke Balls: Defeat Youngster Chris
Poke Balls: Defeat Black Belt Brice
Great Balls: Defeat Picnicker Caitlin
Pinap Berry: Hidden Behind Tree Near Hiker
Post Game
Walkthrough
After defeating the Elite Four and starting the Master Trainers Challenge, you will find just one Master Trainer on Route 9 that you must defeat.
Trainers
Ace Trainer Arnold (Master Trainer): Level 75 Ninetales