Hello VHSenpai,
fast grinding, something like this doesn't exist, later in the game you will unlock the Cerulean Cave, Mt Silver or Dragons Den/Dragons Shrine but at your stage there is no real grinding spot available. My main question is, why is your gyarados just level50, its the 7. gym, it should be higher by now.
Level it up to 70~ and you should be fine for the the gym.
Greetings
I have definitely defeated all trainers around me already and done all quests as well so i am actually quite surprised but it would be nice if you could help me somehow by suggesting a good place to train at the moment. Anyways thanks alot for helping XD :thanks: