go to the gactatic goon near the catching place and follow him until you battle him
which gym leader?
I'm pretty sure you go to Celadon City to try and beat Erica - or was THAT the 3rd Gym Leader?
go and beat the 8th gym
Go to pastoria and battle the gym leader wake
Go to the flower shop next to the gym in Goldenrod City after beating the 3rd gym leader (Whitney normal type) and talk to the lady
you go to sunyshore city and beat that gym leader
After beating the 2nd gym leader you need to see steven in the cave in dewford town if you have not already if you already talked to steven then talk to mr briney and go to slateport city from here go north to mauville city and beat the 3rd gym leader there.
To Blackthorn City.
After defeating the 5th gym leader (Norman) in Flora Sky, the next goal is to get to the 6th gym leader. Go to maulville city and go to the right of the city.
After beating Blue you go to Professor Oak's lab in Pallet Town.
After beating the third Gym Leader (Maylene the Veilstone Gym Leader) in Pokémon Diamond, you then head to Pastoria City to battle the Gym Leader there who is named Crasher Wake.
Go to where Sudowoodo is and talk to a girl in blue, then go back to the flower woman and ask her. She should give you squirtbottle.