Part 1: Starting out — Celadon City HQ (and everything no mission gates)
You get a Rattata, the Pokédex, and HM02 Fly and HM03 Surf from the HQ scientist; the stealing tutorial happens outside. With Fly in hand from minute one, areas that no mission sends you to (Fuchsia, the Safari Zone, Routes 12 to 18, the Power Plant, Celadon itself) are listed at this stage rather than guessed onto a later one.
Starting out — Celadon City HQ (and everything no mission gates) opens 22 areas. There are 90 trainers standing in them. The fights at this checkpoint are Erika, Koga.
Where to go
Celadon City
Wild: Magikarp 100% · Lv 5, Psyduck 99% · Lv 5-40, Grimer 1% · Lv 30-40, Koffing 1% · Lv 30-40
Trainers: Little Girl Susie Lv 3
Pick up: TM19 Giga Drain, TM22 Solarbeam, HM02 Fly, HM03 Surf, Ether, PP Up (hidden), item#0 (hidden), item#0 (hidden) +147 more
Fuchsia City
Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Goldeen 60% · Lv 5-15, Seaking 40% · Lv 20-30 +2 more
Trainers: Bug Catcher Junior Lv 35
Pick up: TM06 Toxic, TM26 Earthquake, Employee Card (gift), Gold Teeth, Max Revive (hidden), Rare Candy (gift), Trainer Card (gift)
Power Plant
Wild: Magnemite 30% · Lv 22-25, Voltorb 30% · Lv 22-25, Pikachu 25% · Lv 22-26, Magneton 10% · Lv 31-34 +1 more
Pick up: TM17 Protect, TM25 Thunder, Elixir, Max Elixir (hidden), Max Potion, Thunderstone, Thunderstone (hidden), Thunderstone +1 more
Rocket Warehouse (area 1)
Wild: Magikarp 100% · Lv 5, Geodude 95% · Lv 5-30, Tentacool 95% · Lv 5-40, Horsea 80% · Lv 5-15 +5 more
Rocket Warehouse (area 2)
Wild: Magikarp 100% · Lv 5, Tentacool 95% · Lv 5-40, Horsea 80% · Lv 5-15, Spearow 30% · Lv 31-32 +8 more
Rocket Warehouse (area 3)
Wild: Magikarp 100% · Lv 5, Psyduck 95% · Lv 5-40, Poliwag 60% · Lv 5-15, Poliwhirl 40% · Lv 20-30 +9 more
Route 12
Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 84% · Lv 15-35, Oddish 35% · Lv 18-22 +6 more
Trainers: Fisherman Elliot Lv 20, Fisherman Ned Lv 20, Fisherman Chip Lv 21, Young Couple Gia & Jes Lv 22, Fisherman Hank Lv 23, Fisherman Andrew Lv 27 +3 more
Pick up: TM48 Skill Swap, Hyper Potion (hidden), Iron, Leftovers (hidden), Rare Candy (hidden)
Route 13
Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 84% · Lv 15-35, Oddish 35% · Lv 18-22 +8 more
Trainers: Bird Keeper Perry Lv 25, Picnicker Gwen Lv 25, Picnicker Susie Lv 25, Beauty Lola Lv 26, Bird Keeper Robert Lv 26, Biker Jared Lv 27 +4 more
Pick up: PP Up (hidden)
Route 14
Wild: Oddish 35% · Lv 18-22, Venonat 30% · Lv 18-22, Ditto 15% · Lv 18-23, Pidgey 10% · Lv 18-22 +2 more
Trainers: Biker Lukas Lv 26, Bird Keeper Mitch Lv 26, Biker Gerald Lv 27, Biker Malik Lv 27, Bird Keeper Beck Lv 27, Bird Keeper Benny Lv 27 +5 more
Pick up: Pinap Berry (hidden), Zinc (hidden)
Route 15
Wild: Oddish 35% · Lv 18-22, Venonat 30% · Lv 18-22, Pidgey 20% · Lv 18-22, Ditto 5% · Lv 21-24 +2 more
Trainers: Biker Ernest Lv 25, Bird Keeper Edwin Lv 26, Beauty Grace Lv 27, Beauty Olivia Lv 27, Biker Alex Lv 27, Bird Keeper Chester Lv 27 +5 more
Pick up: TM18 Rain Dance
Route 16
Wild: Doduo 35% · Lv 18-22, Rattata 30% · Lv 18-22, Spearow 30% · Lv 20-22, Raticate 5% · Lv 23-25
Trainers: Young Couple Lea & Jed Lv 26, Biker Ruben Lv 32
Pick up: HM04 Strength, Leftovers (hidden), Rare Candy (gift), item#0 (gift), item#16385 (gift), item#16385 (gift), item#16385 (gift), item#16385 (gift)
Route 17
Wild: Doduo 35% · Lv 18-22, Spearow 30% · Lv 18-22, Raticate 25% · Lv 20-23, Fearow 5% · Lv 20-23 +1 more
Trainers: Biker William Lv 25, Biker Virgil Lv 26, Cue Ball Jamal Lv 26, Biker Jaxon Lv 27, Biker Nikolas Lv 27, Cue Ball Camron Lv 27 +5 more
Pick up: Full Restore (hidden), Max Elixir (hidden), Max Revive (hidden), PP Up (hidden), Rare Candy (hidden)
Route 18
Wild: Doduo 35% · Lv 18-22, Spearow 30% · Lv 18-22, Fearow 15% · Lv 20-23, Raticate 15% · Lv 20-23 +1 more
Trainers: Bird Keeper Jacob Lv 27, Bird Keeper Wilton Lv 29, Bird Keeper Ramiro Lv 30, Cue Ball Luke Lv 33, Cooltrainer Julien (1) Lv 34, Cooltrainer Julien (2) Lv 35 +2 more
Pick up: Black Belt (gift)
Route 9
Wild: Rattata 40% · Lv 12-15, Spearow 35% · Lv 12-15, Ekans 25% · Lv 12-15
Trainers: Hiker Alan Lv 16, Picnicker Alicia Lv 17, Camper Chris Lv 18, Bug Catcher Brent Lv 19, Camper Drew Lv 19, Hiker Brice Lv 19 +3 more
Pick up: TM40 Aerial Ace, Burn Heal, Chesto Berry (hidden), Ether (hidden), Rare Candy (hidden)
Safari Zone (Center)
Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Goldeen 60% · Lv 5-15, Seaking 40% · Lv 20-30 +12 more
Safari Zone (East)
Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Goldeen 60% · Lv 5-15, Seaking 40% · Lv 20-30 +12 more
Safari Zone (North)
Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Goldeen 60% · Lv 5-15, Seaking 40% · Lv 20-30 +12 more
Safari Zone (West)
Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Goldeen 60% · Lv 5-15, Seaking 40% · Lv 20-30 +12 more
Team Rocket HQ (Celadon City)
Wild: Magikarp 100% · Lv 5, Tentacool 95% · Lv 5-45, Horsea 80% · Lv 5-15, Seel 40% · Lv 43-47 +9 more
Trainers: Burglar Cain Lv 37
Fuchsia City Gym
Trainers: Juggler Kirk Lv 31, Tamer Edgar Lv 33, Juggler Nate Lv 34, Juggler Shawn Lv 34, Tamer Phil Lv 34, Juggler Kayden Lv 38 +1 more
Safari Zone
Trainers: Pokémaniac Elvin Lv 35
Celadon City Gym
Trainers: Lass Kay Lv 36, Beauty Bridget Lv 37, Cooltrainer Mary Lv 37, Lass Lisa Lv 37, Picnicker Tina Lv 37, Beauty Tamia Lv 38 +2 more
★ Erika — Celadon City Gym
| Pokémon | Moves | |
|---|---|---|
 | Tangela Lv 37 | Knock Off Stun Spore Nature Power Giga Drain |
 | Parasect Lv 38 | Fury Cutter Spore Slash Growth |
 | Exeggutor Lv 37 | Stomp Zen Headbutt Egg Bomb Wood Hammer |
 | Victreebel Lv 38 | Sleep Powder Sweet Scent Razor Leaf Leaf Tornado |
 | Vileplume Lv 39 | Giga Drain Aromatherapy Stun Spore Poisonpowder |
★ Koga — Fuchsia City Gym
| Pokémon | Moves | |
|---|---|---|
 | Tentacruel Lv 40 | Acid Spray Barrier Water Pulse Poison Jab |
 | Weezing Lv 40 | Haze Dark Pulse Sludge Bomb Explosion |
 | Golbat Lv 43 | Air Cutter Acrobatics Mean Look Poison Fang |
 | Venomoth Lv 39 | Psybeam Sleep Powder Gust Signal Beam |
 | Muk Lv 41 | Poison Jab Curse Screech Sludge Bomb |
This game's documentation doesn't say where 4 of its 339 fights happen, so those trainers are on no part of this walkthrough; they are all on the Trainers page.