Job-based abilities can prove decisive in battle, so be sure to use them well. You'll also need to make sure you regularly check the abilities screen to see if your characters have any new ones they can use.
Tent in stock
Make sure you have a tent in stock whenever you venture out into the wilderness - during some of the longer dungeons, you'll need one to rest in and restore your party's stamina.
Weapons
If you have a lot of weapons and armour in your collection, try tapping the 'optimise' button on each character's equipment screen. This automatically selects the best combination and saves you a lot of time. It's especially important to do this when switching job types, as some equipment can't be used by certain classes.