Walkthrough
Connected to Route 12 is Route 13, another long path full of both Wild Pokemon and Trainers. Make sure you have plenty of healing Items to take care of your Pokemon, because Fuchsia City is still a long ways away.
Wild Pokemon
Grasses:
Pidgey (20%): Levels 33-38
Pidgeotto (20%): Levels 33-38
Bellsprout (15%): Levels 33-38
Weepinbell (15%): Levels 33-38
Krabby (15%): Levels 33-38
Farfetch'd (10%): Levels 33-38
Kingler (5%): Levels 33-38
Grass - Special Spawns:
Chansey: Levels 33-38
Waters:
Tentacool (30%): Levels 33-38
Horsea (30%): Levels 33-38
Magikarp (30%): Levels 33-38
Tentacruel (5%): Levels 33-38
Seadra (5%): Levels 33-38
Sky:
Pidgey (60%): Levels 3-56
Pidgeotto (35%): Levels 3-56
Pidegot (5%): 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
Camper Nash: Level 37 Sandshrew, Level 37 Sandslash
Picnicker Susie: Level 37 Jigglypuff, Level 37 Weepinbell
Beauty Lola: Level 37 Chansey
Ace Trainer Kite: Level 39 Graveler, Level 39 Magneton, Level 40 Haunter
Bird Keeper Robert: Level 39 Doduo, Level 39 Pidgeotto
Camper Perry: Level 37, Level 37 Nidorino
Beauty Sheila: Level 37 Eevee, Level 37 Persian
Bug Catcher Milo: Level 36 Scyther, Level 36 Pinsir
Picnicker Gwen: Level 37 Raticate, Level 37 Golduck
Punk Guy Jared: Level 38 Golbat
Obtainable Items
Great Balls: Defeat Camper Nash
Great Balls: Defeat Picnicker Susie
Poke Balls: Defeat Beauty Lola
PP Up: Near Ace Trainer Kite (Requires Chop Down)
Ultra Balls: Defeat Ace Trainer Kite
Poke Balls: Defeat Bird Keeper Robert
Great Balls: Defeat Camper Perry
Full Heal: Near Camper Perry
Poke Balls: Defeat Beauty Sheila
Poke Balls: Defeat Bug Catcher Milo
Golden Pinap Berry: Hidden Near Picnicker Gwen
Great Balls: Defeat Picnicker Gwen
Silver Nanab Berry: Hidden In Corner Near Picnicker Gwen
Poke Balls: Defeat Punk Guy Jared
Post Game
Walkthrough
After defeating the Elite Four and starting the Master Trainers Challenge, you will find a couple of Master Trainers on Route 13. In total, there will be two Master Trainers to defeat.
Trainers
Bug Catcher Kenny (Master Trainer): Level 65 Kahuna
Swimmer Arianna (Master Trainer): Level 75 Seaking