after getting the the second badge go to the house which the team rocket robbed come to the other side you will see a man battle him and get TM dig. Then you can see a small way pass through it you will see some trainers battle them and keep going you will come to the next city battle the gym leader he uses electric type pokemons note you need the hm cut to get inside the gym you can get it in the ss anne talk to the captain .
The sixth gym badge (the Marsh badge) is located at Saffron City's gym. It is in Gym Leader Sabrina's possession, so you have to defeat her to obtain it.
in Viridian city. the one that was locked.
the one you get from the gym in fuschia city.
After you beat the gym, you must leave, heal ur pokemon, then go back and talk to the leader and she should give you the badge
The marsh badge is in the saffron city gym you must beat Sabrina the gym leader to get it, but to do that you must beat team rocket in the silph co building.
the boulder badge from brock
The fifth Gym Leader in Pokemon LeafGreen is Koga, the leader of Fuschia City's Gym. He specializes in Poison-type Pokemon and hands out the Soul Badge.
The sixth gym badge (the Marsh badge) is located at Saffron City's gym. It is in Gym Leader Sabrina's possession, so you have to defeat her to obtain it.
Open the door and challenge the gym leader.
Beat Giovanni at viridian city's gym.
in Viridian city. the one that was locked.
it is Mauville gym
In cerulean cities gym you must beat the leader misty to get the cascade badge.
Get the 7th or 8th gym badge, and its in the Power Plant.
Its in Viridian City, the Earth Badge, vs. Giovanni
You have to defeat Erika.
You can get it from the Viridian City GYM. Good Luck!