The best moves for Gyarados in FireRed, LeafGreen, Ruby, Sapphire, and Emerald is this moveset that relies on Gyarados' high Attack Stat, since the Physical/Special split hasn't taken effect on the Gen III games.
Dragon Dance
Hyper Beam
Earthquake
Thrash
The best water type would be Kyogre but you can't get it in leafgreen you need to get one from sapphire or emerald other than that the best water Pokemon is blastoise.
Gyarados is probably the best, it is evolved magicarp.
an electric type.Best found at amp plains.
Charmander, high defense,high attack
Moltres Charizard Arcanine Ninetales Rapidash Flareon
Gyarados
yes
During your first battle against Clair, you can use Ice attacks against her Dragonair and Dragon-type attacks against Kingdra. With Gyarados, you can use an attack such as Thunderbolt since Gyarados is 4 times weak to Electric attacks.
The best water type would be Kyogre but you can't get it in leafgreen you need to get one from sapphire or emerald other than that the best water Pokemon is blastoise.
Blastoise is the best but gyarados and cloyster are also very strong
depends what level
Debatable
Gyarados is probably the best, it is evolved magicarp.
Best non-legendary water pokemon would be Gyarados. Best legendary water pokemon is Kyogre.
GYARADOS
You can catch Moltres at Mt. Ember Peak in FireRed.
THE yellow pokemon :) lol