In the light house!
The first gym in Pokemon diamond is in Oreburgh City
The PokÃ©mon the second Gym Leader has in "Diamond" are Cherubi, Turtwig and Roserade.
The 6th gym leader is in Canalave City.
you beat the gym leader
He is in the lighthouse
by winning a contest and by defeating the pastoria gym leader
just beat the fourth gym leader
It is Candace, The Ice-Type Gym Leader.
Go to the lighthouse and the Gym leader should be there.
Hearthome city and battle the gym leader
a gym leader can't teach a Pokemon that move but you have to defeat the 6 gym leader in order to teach that move
You have to beat her Pokemon.
in the forest by the 2 gym leader
go into oreburgh mine and talk to gym leader
in vilstone city not hearthome that's the fifth gym leader