Question: what do you do after you beat team rocket in celadon city?
Answer: Once you beat Erika, you get your hands on the Rainbow Badge, allowing Pokémon up to level 50 to listen to you. She also gives to you TM53 - Mega Drain. After defeating the Celadon City Gym, head on over to the Game Corner again and take on Team Rocket's Hideout if you haven't already!