Pokémon Gold and Silver/Indigo Plateau

Here, your journey will be half way over, the Pokémon League Elite Four awaits, it is recommended that first, you get some powerful Pokémon on your team (>lvl. 50) then go in.

You may also want some items, the Center is also a Mart and the person with the can teleport you back to New Bark Town.

Recommended Pokémon
It is recommended to have at least one of these:
 * Ice type Pokémon (with a water move)
 * Dewgong w/ Surf, Whirpool or Waterfall
 * Cloyster w/ Clamp, Surf or Whirlpool
 * Lapras w/ Water Gun, Hydro Pump, Surf or Whirlpool
 * Sneasel w/ Surf
 * Electric type Pokémon
 * Fire type Pokémon
 * Rock type Pokémon
 * Fighting type Pokémon
 * Psychic type Pokémon

Elite Four Will



 * Moves: Quick Attack, Future Sight, Psychic, Confuse Ray Use your Ice/Electric/Dark Pokémon
 * Moves: Psychic, Egg Bomb, Leech Seed, Reflect Use your Fire/Flying Pokémon
 * Moves: Ice Punch, Double Slap, Psychic, Lovely Kiss Use your Fire Pokémon
 * Moves: Psychic, Body Slam, Curse, Amnesia Use your Electric/Grass Pokémon
 * Moves: Psychic, Quick Attack, Future Sight, Confuse Ray Use your Ice/Electric/Dark Pokémon

Afterwards, heal up, and re-organize your Pokémon so that you have your Psychic Pokémon leading

Elite Four Koga



 * Moves: Spider Web, Double Team, Baton Pass, Giga Drain Use your Psychic or Fire Pokémon.
 * Moves: Gust, Supersonic, Toxic, Psychic Use your Psychic Pokémon, Water, or Fire Pokémon.
 * Moves: Spikes, Swift, Protect, Explosion Use your Fire Pokémon.
 * Moves: Sludge Bomb, Minimize, Toxic, Acid Armour Use your Psychic Pokémon.
 * Moves: Wing Attack, Double Team, Toxic, Quick Attack Use your Psychic or Electric Pokémon.

Afterwards, be sure to lead with a Psychic type

Elite Four Bruno



 * Moves: Quick Attack, Dig, Detect, Pursuit Use your Psychic Pokémon/Flying Pokémon/Water
 * Moves: Ice Punch, Fire Punch, Thunder Punch, Mach Punch Use your Psychic Pokémon/Flying Pokémon/Water
 * Moves: Double Kick, Foresight, Hi Jump Kick, Swagger Use your Psychic Pokémon/Flying Pokémon/Water
 * Moves: Rock Slide, Foresight, Cross Chop, Vital Throw Use your Psychic Pokémon/Flying Pokémon/Water
 * Moves: Rock Slide, Sandstorm, Earthquake, Bind Use your Ice Pokémon's Water Move

Once beaten, be sure to place a fighting-type as your lead.

Karen



 * Moves: Faint Attack, Confuse Ray, Mean Look, Sand Attack Use your Fighting Pokémon. Do not use rock smash.
 * Moves: Stun Spore, Acid, Petal Dance, Moonlight Use your Fire Pokémon
 * Moves: Lick, Spite, Curse, Destiny Bond Use your Psychic Pokémon
 * Moves: Faint Attack, Whirlwind, Pursuit, Quick Attack Use your Ice Pokémon
 * Moves: Crunch, Flame Thrower, Roar, Pursuit Use your Water Pokémon

Once finished, place an electric into the lead because Lance's first Pokémon is a gyarados.

Champion Lance



 * Moves: Rain Dance, Surf, Flail, Hyper Beam Use your Electric Pokémon
 * Moves; Twister, Thunderwave, Hyper Beam, Blizzard Use your Ice Pokémon
 * Moves: Twister, Thunderwave, Thunder, Hyper Beam Use your Ice Pokémon
 * Moves: Safegaurd, Outrage, Fire Blast, Hyper Beam Use your Ice Pokémon
 * Moves: Flame Thrower, Slash, Wing Attack, Hyper Beam Use your Water Pokémon
 * Moves: Rock Slide, Ancient Power, Wing Attack, Hyper Beam Use your Ice or Rock Pokémon, doesn't matter which

After defeating the Elite Four and Lance, the end credits roll. However, your journey is not over yet, you still have 8 more badges to get...

Rival (after you defeat the Elite Four on Mondays and Wednesdays)

 * (lvl. 50, 2227/2238/2275 EXP)
 * (lvl. 50, 2227/2238/2275 EXP)
 * (lvl. 50, 2227/2238/2275 EXP)
 * (lvl. 50, 2227/2238/2275 EXP)
 * (lvl. 50, 2227/2238/2275 EXP)
 * (lvl. 50, 2227/2238/2275 EXP)