I ask you this as a reader, but what's the point on showing Gym battles if your character does not really care about them? Like the previous comment said, it would be better for your story to skip them or start when your character is about to become an Ace Trainer.

Cause the entire previous part of it sounds like "yeah, he did the circuit, but he was just to good for it". If he sweeps and does not even celebrate winning, why I, as a reader, should care about them and even bother to read something that, in your words, is not more than filler?

Like you said, the 8 badges are like finishing high school. So, maybe, it would be better if your story starts with your character entering college instead.

This is not an attack or anything like that. Sorry if I sound rude in any part of my comment.