Jangowuzhere
Banned
I'm in this same spot. I'm not sick of the game or anything yet, but I am at a bit of a loss about how to proceed. Similar to your experience, I feel pretty underleveled at 13 and I don't know if I should be grinding lower level monsters or picking up more quests or what have you. I played Xenoblade, but that is way more linear and simpler mechanically than this. I literally feel old trying to understand all the mechanics and systems going on in this game sometimes.
The fastest way to level up is literally grind slightly higher level monsters. The vast majority of quests give you absolutely nothing of value. They give you like no experience and barely any money. It's better to focus on doing affinity quests, exploring, and story missions. Go out and grind when the game stupidly gates your story progress.
If you spend too much time doing anything else, then you'll end up getting bored.