Gym Leaders

Taken from: Lavender Town

Brock

Location: Pewter City
Pokemon:
Geodude Lvl. 12 
Onix Lvl. 14 

He is very easy but only if you have a Squirtle or a Bulbasaur. If you don't have one, then you're in trouble. That's not really fair because the only way to totally waste Brock is if you chose a Squirtle or Bulbasaur at the very beginning of the game.

You should definately not send out your Pikachu or Charmander. But if you do, don't use fire or thunder type attacks because rock Pokemon are very strong against those. Especially don't use Thunder attacks because it will have no effect.

When you defeat Brock, you are rewarded with the Boulder Badge, TM 34 (Bide), and you can use Flash outside of battle.

Misty

Location: Cerulean City
Pokemon:
Staryu Lvl. 18 
Starmie Lvl. 21 

Misty is a bit easier than Brock but not by much. She is a fairly difficult leader to beat even though she only has two Pokemon. It's because its early in the game and most people havent raised their Pokemon to high enough levels yet.

The best Pokemon to use at this point in the game are a Pikachu if you caught one in the Viridian Forest and a Bulbasaur if you chose that one at the beginning. If you don't have either of those two, it would be a good idea to come back some other time when your Pokemon have reached higher levels. Even then she still may be difficult.

The fist Pokemon she sends out is Staryu. It's fairly easy to beat. It mostly uses tackle. I wasted it in about two or three moves. I was using a Pikachu's Thundershock.

The next Pokemon she will send out is Starmie. This one is really hard. You have to watch out for Bubble Beam. That one really got me. I always had troule beating Starmie.

Once you defeat her, she rewards you with the Cascade Badge, TM 11 (Bubble Beam) and Pokemon up to level 30 will obey you.

Lt. Surge

Location: Vermilion City
Pokemon:
Voltorb Lvl. 21
Pikachu Lvl. 18 
Raichu Lvl. 24 

First before you battle Lt. Surge, you have to find 2 switches which open the doors. This is very frustrating for me. I know they are supposed to be right next to each other, but I always seem to choose the wrong one and then it starts all over again.

He's pretty easy to beat. Just use a ground type Pokemon against him. A diglett would be excellent. Just wip him out with dig.

Definately don't use a water Pokemon against him, because it will be wasted!

After you defeat him, he rewards you with TM 24 (Thunderbolt), all your Pokemon's speed increases a little, and you can use Fly outside of battle.

Erika

Location: Celadon City
Pokemon:
Victreebel Lvl. 29 
Tangela Lvl. 24 
Vileplume Lvl. 29 
A fire Pokemon would be very good to use against Erika

Sabrina

Location: Saffron City
Pokemon:
Kadabra Lvl. 38
Mr. Mime Lvl. 37 
Venomoth Lvl. 38 
Alakazam Lvl. 43 
Sabrina is probably the most difficult gym leader in the game.

Koga

Location: Fuchsia City 
Pokemon:
Koffing Lvl. 37 
Muk Lvl. 30 
Koffing Lvl. 37 
Weezing Lvl. 43 
He's pretty easy to beat. Just bring out your strongest Pokemon.

Blaine

Location: Cinnabar Island 
Pokemon:
Growlithe Lvl. 42 
Ponyta Lvl. 40 
Rapidash Lvl. 42 
Arcanine Lvl. 47 
Any water type Pokemon should take down Blaine in no time.

Giovanni

Location: Viridian City 
Pokemon:
Rhyhorn Lvl. 45 
Dugtrio Lvl. 42 
Nidoqueen Lvl. 43  
Nidoking Lvl. 45 
Rhydon Lvl. 50 
Another water type Pokemon should work pretty good here.