You don't know what you don't know.
And you'll never know until you get through the barrier that stops you from knowing.
Even background knowledge counts what matters is keep taking that next step and never stand still.
If MC goes all out then he'd be Gilgamesh type throwing stored items to enemies. Or at least that's what the last page suggests. He looks like he has better proficiency than the "random bullshit go chucker" king of heroes tho