you have to go to the light house to the southeast of town.
~Jayfeather
you got to the top of the sunnyshore light house and talk to the blond guy he is the gym leader then you can face him.
Go to the lighthouse and the Gym leader should be there.
In Sunnyshore City.
in sunnyshore
by doing everything else
Gary isnt a gym leader
That'd be Volkner who remains the Gym Leader there.
If your in sunnyshore city then just go to the gym and battle him.
his is in the lighthouse in sunnyshore city
go to sunnyshore city
go to sunnyshore city
catch dialga the go to sunnyshore