Well,the 3rd gym leader is maylene. She is also gym leader number 3 in diamond and pearl.So no need to worry.
In Veilstone City
Byron in Canalave City is the sixth gym leader in Pokemon Diamond. He specializes steel-type. His 3 pokemons are Bronzor, Steelix, and Bastiodon.
The 6 gym leader in at Canalave City. the gym after the hearthome City gym!!!!!
The 6th gym leader is in Canalave City.
The first gym in Pokemon diamond is in Oreburgh City
It is Candace, The Ice-Type Gym Leader.
Go to the lighthouse and the Gym leader should be there.
by winning a contest and by defeating the pastoria gym leader
just beat the fourth gym leader
his name is leader byron.
The Pokémon the second Gym Leader has in "Diamond" are Cherubi, Turtwig and Roserade.