You'll start in your room. Exit the room and talk to your mom to get
your Pokégear. Your mom will also ask you for the time and date. Tell her and get out of the
house. Go meet Professor Elm working in his lab. He'll tell you to get pick a Pokemon and
will ask you to run an errand for him.
Return back to Cherrygrove City. The Pokémon battle will be finished so you can continue going north. You'll now come to Violet City. Explore a little bit and heal up. Then, go to the Sprout Tower and beat the elders to get HM5, Flash. Your rival will be there to greet you. He won't challenge you though.
Now, go to the
gym. The gym leader is Falkner. He is a flying type specialist. His
Pokémon include a Hoothoot and a Pidgeotto. If you chose a Chikorita as your
starting Pokémon, you'd better use reflect or Falkner will knock you out pretty
quick. When you beat him, he'll give you a Zephyr Badge.
Union Cave has only one floor that you have to pass through, so it's not very complicated. All you have to do is follow the main path to get to the exit. Be careful, though. There are several trainers lurking about.
After you get through Union Cave, you'll arrive at Azalea Town. Azalea Town has a gym, but it will be blocked off by Team Rocket. You have to go to the Slowpoke Well and defeat the Team Rockets to access the gym.
When you do defeat all the Rockets, you can finally enter the gym. The gym leader is Bugsy. As you might guess, her specialty is bug type Pokémon. Her arsenal includes a Kakuna, Metapod, and a Scyther. Be careful with her Scyther. It's really tough. When you beat her, she'll hand over her Hive Badge.
After the battle, you can head on to Ilex Forest. Your rival will challenge you when you try to get to the entrance. His Pokémon have gotten significantly stronger, so prepare yourselves before battling.
Next, go inside Ilex Forest. You'll a tree that will be blocking your path. Help the boy find his Farfetch'd, so he'll give you HM1 Cut. You have to use cut to get out of Ilex Forest and into Goldenrod City.
Lots of sights await you in Goldenrod City. There's the Radio Station, the Game Corner, the big Dept. Store, and the Underground Path. First, you can go to the Underground Path to find the Coin Case. Then you can take it to play in the Game Corner, if you want.
There is also a gym in Goldenrod City. The leader of the gym is Whitney. She specializes in normal type Pokémon. This includes a level 18 Clefairy and a level 20 Miltank. When you beat her, she'll give you a Plain Badge (I think).
When you do beat Whitney, go to the house east (right) of the gym. The person watering the flowers will give you a Squirtbottle. Use the Squirtbottle on the Sudowoodo blocking the path to make it challenge you to a battle. Remember, this is the only one in the game, so try to capture it.
Now, go on to Ecruteak City. Defeat all the Kimono Girls to earn HM4 Surf. Then, go to the Burned Tower. You'll meet your rival there. Beat him and set the ledgendary Pokémon loose. You can now catch them when you meet them in the wild.
Next, go to the Ecruteak City gym. The leader, Morty, has ghost type Pokémon. I don't know what they are, though. Anyways, after you beat him, he'll give you a Fog Badge for your collection.
Now, go to Olivine City and climb the Lighthouse. There are some trainers there, too. On the top floor, Jasmine, the Olivine City gym leader will be there. Talk to her. She'll tell you the Lighthouse Pokémon (an Ampharos) is sick. Then she'll tell you to get the Secret Potion from Cianwood City.
Since she told you this, go to Cianwood City and get the medicine. While you're there, you'll encounter a gym. The gym leader is Chuck. Chuck has fighting type Pokémon. Beat him to get the Storm Badge and HM2 Fly. Teach fly to your Pokémon and fly back to Olivine City to deliver the medicine. Jasmine will then return to the gym.
Jasmine is now ready for a battle. Her Pokémon are steel types. Watch out, they're very tough. Use a fire type to have a fighting chance. After you beat her, she'll give you the Mineral Badge.
Go back to Ecruteak City. From there, go to Mahogany City. You'll pass through Mt. Mortar. If you don't want to go to Mt. Mortar, you can just surf around it.
When you come to Mahogany City, you'll see that the entrance to the gym it blocked by a Team Rocket member. You have to go up to the Lake of Rage and fight or catch the mysterious Red Gyrados. Then Lance will appear. Talk to him to help him investigate the unusual sounds the radio has been broadcasting. It turns out that Team Rocket has taken over the city. Beat them to get HM6 Whirlpool.
Now Team Rocket has taken over Goldenrod City as well. This time, Lance won't be there, so you'll have to face them alone. Go to the Underground Path to the suspicious looking door. Use the Card Key (I think) to open it up. Team Rocket members are everywhere! Beat them all to rescue the Radio Station Director. He'll thank you and will give you a Gold/Silver Feather. That feather is for making one of the legendary birds appear.
Now, go back to Mahogany City. The person blocking the gym entrance will be gone. Enter the gym. You'll find the floor covered in ice. As you might have guessed, the gym leader, Pryce, has ice type Pokémon. Electric type Pokémon work well against him. When you defeat him, he'll give you a badge (I don't know which).
Go through ice Ice Cave, now that you've beat him. It leads to Blackthorn City. A den is at the back of the gym, but you can't enter it yet. You have to beat the gym leader, Clair, to do so.
Clair's specialty is dragon type Pokémon. Dragon types don't have any specific weaknesses (except for ice), so they can make it pretty tough. Clair is the final gym leader you have to beat to enter the Pokémon League. But after you beat her, she won't give you a badge. Instead, she'll challenge you to find the Dragon's Fang in the Dragon's Den. If you find it, she'll finally give you a badge (I don't know which).
Now you're on your way to the Pokemon League! Return to New Bark Town and surf to the other side of the water. You'll enter Kanto. Follow the path until you reach Victory Road. At the end of Victory Road, you'll meet your rival. Beat him to get to the Elite 4 and the Pokémon League HQ.
If you manage to beat the Elite 4 and Lance, you'll get to see the credits. Then, the game will restart. But don't think your journey is over, though. Choose to continue and you'll find that Professor Elm will call to give you the S. S. Aqua ticket. Fly to Olivine City. The S. S. Aqua will pull into the port.
When you aboard the ship, you'll need to find a little lost girl. You can only get out once you have found her. The girl is in the Captain's room. Talk to her to get her to come back. After you do, the S. S. Aqua will come to a stop in Vermillion City.Vermillion City is in the Kanto, the old Pokémon world. You'll see a gym there, so go in there to battle for a badge.
From Vermillion City, you can get to Saffron City. Saffron City lives a girl nicknamed Copycat. She has lost her Pokédoll. It is in Vermillion City, so go back and look for it. After you bring it back to her, she'll give you a Pass for the Magnet Train.
But the Magnet Train has lost its power. It seems like the Power Plant is down. Go to the Power Plant, behind Rock Tunnel, and talk to the guy fixing it. He'll say that a Machine Part was stolen. Now, go to Cerulean City. Look in the gym. The missing Machine Part is in the water somewhere. When you find it, return to the Power Plant and give it to the same guy. Now the Magnet Train has power again.
It's time to go back and explore all of the cities and towns of Kanto. But you'll find it impossible to get to Pewter City. Go to Lavender Town to get the Kanto radio card extension. Fly to Vermillion City and turn your new radio extension to the Pokéflute channel to wake up the sleeping Snorlax. Battle and catch it to access the Diglett's Tunnel.
Follow the Diglett's Tunnel to a route between Pewter City and Viridian City. Now you can finally get to Pallet Town, the place where Ash first started his Pokémon quest.
In Pallet Town, there is a Pokémon Lab. Professor Oak works there. Go see him. He'll look to see if you have all the Kanto badges. If you do, he'll let you go to Silver Cave.
Silver Cave is home to all the highest level Pokémon. It is also where Ash (name is changed to Red) is training. Red is the final battle that you have to face. He is waiting for you in a small room in a cave floor. Walk up to him. He'll challenge you to a match. His Pokémon party includes a Pikachu, Venusaur, Charizard, Blastoise, Espeon, and Snorlax. They're all around level 70 to 80. Good luck!