Walkthrough
After defeating the Pewter City Gym, you can proceed on Route 3 just east of the city. Route 3 is full of both Wild Pokemon and Trainers alike, and it will lead you straight to the western side of Route 4.
Wild Pokemon
Grasses:
Rattata (40%): Levels 3-8
Spearow (40%): Levels 3-8
Ekans (20%): Levels 3-8
Grasses - Special Spawns:
Charmander: Levels 3-8
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
Coach Trainer Kareem: Level 11 Bulbasaur
Lass Janice: Level 6 Oddish
Youngster Calvin: Level 6 Spearow
Camper Victor: Level 7 Nidoran M
Picnicker Robin: Level 7 Nidoran F
Youngster Ben: Level 6 Rattata
Bug Catcher Greg: Level 5 Kakuna
Obtainable Items
Revive: Defeat Coach Trainer Kareem
Poke Balls: Defeat Lass Janice
Poke Balls: Within Bush Near Lass Janice
Poke Balls: Defeat Youngster Calvin
Potion: Near Youngster Calvin
Great Balls: Defeat Camper Victor
Great Balls: Defeat Picnicker Robin
Lure: Within Bush Near Picnicker Robin
Poke Balls: Defeat Youngster Ben
Poke Balls: Defeat Bug Catcher Greg
Razz Berry: Within Bush Near Bug Catch Greg (Found By Pokemon)
Revive: Grasses South Of Pokemon Center
Post Game
Walkthrough
After defeating the Elite Four and starting the Master Trainers Challenge, you will find just one Master Trainer within Route 3.
Trainers
Ace Trainer Ronnie (Master Trainer): Level 65 Nidoran F