This is a quick and dirty walkthrough, all the way from the opening to the ending credits. I've included maps of almost every location, and marked the location of every treasure I found. I've also included some information on how to unlock the next part of the story in some places, as the translations aren't always that helpful.
Because there's so much difference between Easy and Normal difficulty, and so many classes and characters to choose from, I don't go into too much strategy for boss battles. For the most part I've tried to record the attacks or spells that bosses used against me, and offer suggestions on how to make the battle easier. But ultimately, you'll need to find your own boss strategies.
However, the way this game is set up, any time your party dies in battle, you can opt to watch a 15 or 30-second ad and have your entire party revived, and continue the battle. (Note that you'll be revived to full HP, but it won't replenish your MP.)
If you play the game on Normal difficulty, you'll want to upgrade your weapons and armor pretty regularly, and as soon as possible, you should also cycle your characters through as many job classes as possible. The stat bonuses and the extra spells they'll learn will make a huge difference.
Otherwise, relax, enjoy the game, and at least know that any time you do get stuck, you can find the answer you need within the pages of this walkthrough!