Cerulean City
If you want a faster way to travel, the Bike Shop has just the thing for you...for the low low cost of only...$1,000,000? You will also find a house that has been ransacked by Team Rocket, but you won't be able to enter until after you defeat Misty and cure Bill (on Route 25).
Pokemon Mart
*Pokeball--------200
*Potion----------300
*Repel-----------350
*Antidote--------100
*Burn Heal-------250
*Awakening------200
*Paralyze Heal---200

Cerulean City Gym
Misty is the leader of the Cerulean Gym, and she loves water Pokemon. You can tell because she has converted the Gym into a pool! Two other Trainers will challenge you before you can take on Misty, but Pikachu or Bulbasaur can blow them out of the water.

Vs. Misty Swimsuit clad Misty likes to swim, but she simply loves to battle. She packs Water Pokemon, a Staryu and a Starmite. If you have Bulbasaur or Pikachu, you will win this battle fairly quickly. Misty, rather impressed, will give you her Cascade Badge and a TM 11 for a job well done.

Routes 24 & 25
Pokemon Found: 010 Caterpie, 011 Metapod, 013 Weedle, 014 Kakuna, 016 Pidgey, 043 Oddish (Red), 063 Abra, 069 Bellsprout (Blue)
After you defeat Misty, the path to the north will open up. But before you can go very far, Gary will show up once again to make trouble.

Vs. Gary Gary has added three Pokemon to his arsenal, an Abra, a Rattata, and a Pidgeotto. A heavily built up Pikachu or Bulbasaur (which should have evolved to an Ivysaur by now) has the best chance. Defeat Gary to send him off in a fit.

As you continue onto the bridge, you will be challenged by six members of Team Rocket. Their Pokemon are tough, so return to the Pokemon Center after each battle to heal your monsters. When you defeat all six, you will get a valuable Nugget as a reward. Sell it off to get $5000. Continue to the east where you will find even more Pokemon Trainers. Once you get past them, you will find the Sea Cottage.

Bill the Pokemaniac Poor Bill has turned himself into a Pokemon! If you help him out, Bill will give you a ticket to board the S.S. Anne, a cruiseship for only the best Pokemon Trainers!
Items Found on Routes 24 & 25
*TM 18
*TM 45