You can fight the Kanto Gym Leaders in any order, except Brock, Blaine, and Green/Blue.
You CAN NOT become a Gym Leader in Pokemon HeartGold and SoulSilver or ANY MAIN SERIES POKEMON GAME.
level grind.
In Pokémon HeartGold, you can find the 3rd Gym Leader in Goldenrod City.
Obtain it from a gym leader.
you can take on any gym leader in kanto in any order (excluding blue you have to battle him last)
The gym is in Blackthorn City.The gym leader is Clair.
He has many types.
Brock.
try beating the gym leader
he is the vermillion city gym leader.
first get a ice type Pokemon then go threw the whole gym face gym leader and get the badge
go to the next gym leader.