If you're at ilvl 660, you have gear that will see your adequately through the Dawntrail MSQ until you get your level 100 Job Armor. You won't see better gear until the level 95 dungeon*. The 600 gear and a few dungeon drops will be all you need to get to level 100, you can save all those free gear coffers* for leveling alt-jobs, or selling.

* - of course assuming they follow the same pattern as previous expansions.