Brock

Location: Pewter City

Pokémon: Geodude Lv12, Onix Lv 14

Rewards: Boulder Badge, TM 34

Good Type to Use Against: Water

Misty

Location: Cerulean City

Pokémon: Staryu Lv18, Starmie Lv21

Rewards: Cascade Badge, TM 11

Good Type to use Against: Grass or Electic

Lt. Surge

Location: Vermilion City

Pokémon: Voltorb Lv21, Pikachu Lv18, Raichu Lv24

Rewards: Thunder Badge, TM 24

Good Type to use Against: Ground

Erika

Location: Celadon City

Pokémon: Victreebel Lv29, Tangela Lv24,

Vileplume Lv29

Rewards: Rainbow Badge, TM 21

Good Type to use Against: Fire, Ice, or Poison

Sabrina

Location: Saffron City

Pokémon: Kadabra Lv38, Mr. Mime Lv37,

Venomoth Lv38, Alakazam Lv43

Rewards: Marsh Badge, TM 46

Good Type to use Against: Bug or Ghost

Koga

Location: Fuchsia City

Pokémon: Koffing Lv37, Muk Lv39,

Koffing Lv37, Weezing Lv43

Rewards: Soul Badge, TM 6

Good Type to use Against: Ground or Psychic

Blaine

Location: Cinnabar Island

Pokémon: Growlithe Lv42, Ponyta Lv40,

Rapidash Lv42, Arcanine Lv47

Rewards: Volcano Badge, TM 38

Good Type to use Against: Water or Ground

Giovanni

Location: Viridian City

Pokémon: Rhyhorn Lv45, Dugtrio Lv42,

Nidoqueen Lv43, Nidoking Lv45, Rhydon Lv50

Rewards: Earth Badge, TM 27

Good Type to use Against: Ground or Water