- Do sidequests as they become available, they add a lot of character to the overall story. Sidequests marked with a "+" generally reward you with some sort of permanent upgrade or item recipe.
- There is no postgame where you get to clear up unfinished sidequests, they're meant to be done before the final story mission.
- Mastering an ability allows you to put it in any ability slot.
- Spend AP freely, you can always reset an ability you're not using anymore, and you'll need the AP to upgrade and master those you do.
- You can autosell valuables by pressing the touchpad on the sell menu. It wont sell any of your crafting mats or anything else important.
- There is a vestigial crafting/upgrade system but you don't need to think about it at all. Every time the game tells you there are new crafting recipes available you should go craft the new stronger thing for yourself, unless the game has already given you a stronger piece of equipment for some reason. There is absolutely no reason not to do this.
- There's no reason not to sell your old equipment if you need cash.