Kanto and Mt. Silver

Take the S.S. Aqua to Vermilion. Restore the Power Plant by recovering its stolen Machine Part from Cerulean Gym. The Copycat in Saffron trades the missing Poké Doll from Vermilion's fan club for a Pass, reopening the Magnet Train.

Tune the Pokégear Radio to the Poké Flute channel beside Snorlax to open Diglett's Cave. Kanto's badges can mostly be tackled flexibly, although restoring power and moving Snorlax open key routes. Defeat Blue in Viridian Gym for your sixteenth badge, then speak to Professor Oak. He opens Mt. Silver, where Red waits with a Lv.81 Pikachu and a balanced team of six.