I've heard that the only thing that carries over is:
- Your bracer notebook status (meaning what jobs you solved, so NPC's you've helped before will remember it) - Your Bracer Points. (you apparantly get a reward for importing with max BP) - Estelle's level (everyone else later joins at a predetermined level) It's capped at 40, so if you gain any more levels with her beyond that limit, they'll be lost once you make the jump to the second game.
Apparantly stuff like quartz, items and weapons don't carry over.
Yep, there's no need to get a 'perfect' file on New Game + in order to take advantage of all the carryover bonuses, you can (theoretically) do it on a single playthrough since BP is the only important factor. A minor detail to add is that aside from getting a reward for Max BP you'll also get an item for each Rank of 3 or higher you earned in FC.
Yeah, end the game with all BP and Estelle at Lv40 and you'll have everything that matters for carryover purposes. Not that the level is a huge thing anyways (if you start 'low' you'll catch up really quickly) but it does carry over within limits. Your BP is the big thing.
And just to clarify, your BP doesn't actually carry over. You have 0 BP at the start of SC no matter what. But you get a small reward depending on your BP from your clear file; you need max BP to get the best reward though.
That and the 1 early SC quest requires 1 copy of 6 separate food items and without the 30% increased item drop quartz (needs max BP in FC) to start with it then the item drop rate is only about 5% per item.
If the TC also plays Kiseki the 3rd levels are the only thing that carries over to it but you still do get 2 good accessories by having max BP at the end of SC to transfer over even though the 3rd doesn't use BP/have such quests do to at all.