8 gyms.
You can catch Latias
Get four badges from other gyms.
you find aron in ruby sapphire and emerald you find them in the second gyms c
Rusboro fortree petalburg dewford mauville lavaridge mossdeep sootopolis
Beat the gym leaders and the elite four.
The gyms are at: Rustboro City, Dewford Town, Mauville City, Lavaridge Town, Petalburg City, Fortree City, Mossdeep City, Sootopolis City.
Try to complete the Pokédex.
on the second gyms island the cave that you meet Steven, the hiker at the beginning will give it to you
well in ruby and sapphire you need to beat all gyms and then beat the elite four then it should be open but in emerald you only need to beat the 8 gyms
In total, you must beat four gym leaders before you can face your dad: Roxanne, Brawly, Watson and Flannery.
beat all 8 gyms or in sapphire emerald or ruby you go to team aquas base or you could game shark it
16 gyms 8 in johto and another 8 in kanto.