Part 1: Before any badges
Starting out.
Before any badges opens 8 areas. There are 22 trainers standing in them. The fights at this checkpoint are Rival Blue (Charmander), Rival Blue (Squirtle), Rival Blue (Bulbasaur), and 31 more.
Where to go
Pallet Town
Viridian City
Route 1
Wild: Pidgey 40.3% · Lv 2-5, Rattata 40.2% · Lv 2-4, Coinpur 19.6% · Lv 2-3
Route 2
Wild: Pidgey 35.1% · Lv 3-4, Rattata 19.9% · Lv 4, Coinpur 15.3% · Lv 3-5, Caterpie 14.9% · Lv 3-4 +1 more
Route 22
Wild: Magikarp 60% · Lv 6-7, Orfry 41% · Lv 5-7, Rattata 29.7% · Lv 3-4, Nidoran♀ 20.3% · Lv 4 +3 more
Trainers: ★ Rival Blue (Charmander) — rematch Lv 9, ★ Rival Blue (Squirtle) — rematch Lv 9, ★ Rival Blue (Bulbasaur) — rematch Lv 9, ★ Rival Blue (Pikachu) — rematch Lv 9, ★ Rival Blue (Eevee) — rematch Lv 9, ★ Rival Blue (Charmander) — rematch 6 Lv 53 +4 more
Viridian Forest
Wild: Caterpie 29.7% · Lv 4-5, Weedle 29.7% · Lv 4-5, Pidgey 15.2% · Lv 4, Gentlarva 9.8% · Lv 5 +4 more
Trainers: Bug Catcher #1 Lv 6, Bug Catcher #2 Lv 7, Bug Catcher #3 Lv 9
Oaks Lab
Trainers: ★ Rival Blue (Charmander) Lv 5, ★ Rival Blue (Squirtle) Lv 5, ★ Rival Blue (Bulbasaur) Lv 5, ★ Rival Blue (Pikachu) Lv 5, ★ Rival Blue (Eevee) Lv 5
Viridian Pre Gym
Trainers: ★ Yujirou Lv 8, ★ Yujirou — rematch Lv 64, Student #1 Lv 4, Student #2 Lv 6
★ Rival Blue (Charmander) — Oaks Lab
| Pokémon | Moves | |
|---|---|---|
 | Squirtle Lv 5 |
★ Rival Blue (Squirtle) — Oaks Lab
| Pokémon | Moves | |
|---|---|---|
 | Bulbasaur Lv 5 |
★ Rival Blue (Bulbasaur) — Oaks Lab
| Pokémon | Moves | |
|---|---|---|
 | Charmander Lv 5 |
Also fought around here
This game's documentation doesn't say where 18 of its 471 fights happen, so those trainers are on no part of this walkthrough; they are all on the Trainers page. It also doesn't say when Faraway Island Inside, Digletts Cave open up, so they are in no part above; each has its own route page.