Walkthrough
At the end of Route 13 is Route 14, yet another long path full of Pokemon Trainers and Wild Pokemon. This is the halfway point to Fuchsia City, with only Route 15 left afterwards.
Wild Pokemon
Grasses:
Oddish(FireRed)/Bellsprout(LeafGreen) (35%): Levels 22-26
Venonant (30%): Levels 24-26
Ditto (15%): Level 23
Pidgey (10%): Level 27
Pidgeotto (5%): Level 29
Gloom(FireRed)/Weepinbell(LeafGreen) (5%): Level 30
Pokemon Trainers
Bird Keeper Carter: Level 28 Pidgey, Level 28 Doduo, Level 28 Pidgeotto
Bird Keeper Mitch: Level 26 Pidgey, Level 26 Spearow, Level 26 Pidgey, Level 26 Fearow
Bird Keeper Marlon: Level 28 Spearow, Level 28 Doduo, Level 28 Fearow
Bird Keeper Beck: Level 29 Pidgeotto, Level 29 Fearow
Bird Keeper Donald: Level 33 Farfetch'd
Bird Keeper Benny: Level 29 Spearow, Level 29 Fearow
Biker Gerald: Level 29 Koffing, Level 29 Muk
Biker Malik: Level 29 Koffing, Level 29 Grimer
Biker Isaac: Level 28 Grimer, Level 28 Grimer, Level 28 Koffing
Biker Lukas: Level 26 Koffing, Level 26 Koffing, Level 26 Grimer, Level 26 Koffing
Twins Kiri & Jan: Level 29 Squirtle, Level 29 Charmander
Pokemon Trainers - VS Seeker Rematch
Bird Keeper Marlon: Level 30 Fearow, Level 30 Doduo, Level 30 Fearow
Bird Keeper Marlon: Level 48 Fearow, Level 48 Wartortle, Level 48 Fearow
Bird Keeper Benny: Level 32 Fearow, Level 32 Fearow
Bird Keeper Benny: Level 49 Fearow, Level 49 Fearow
Biker Lukas: Level 47 Koffing, Level 47 Koffing, Level 47 Muk, Level 47 Weezing
Items
Zinc: ItemFinder
Pinap Berry: ItemFinder