Don't bother wasting time completing all of the quests, NG+ resets all quest progress.
The ideal way to handle it is to beat the main story first, then do the following things:
-Get all Rare Blades so pulling for the NG+ exclusive Blades is easier.
-Get 99 of every core type after that so you can potentially get all of the randomly pulled NG+ Blades early on.
-Get your favourite Blades to S+ Trust.
-Beat the Lv. 117 Superboss, as beating him gives you access to 10 Dilation Chips, the best Tank/Healer Chip in the game. You can only get these once per playthrough, but can get them again in a NG+ run.
-Complete KOS-MOS's Blade Quest, as the reward is Blade Combo Boost VI and Fast Blade Switch VI Aux Cores. While these are probably gonna be more readily available in a future update, right now they're the only Level VI Aux Cores in the game. And like the Dilation Chips, they are a once per playthrough thing.
-Get to Merc Lv. 5.
-Get Development Lv. 5 in all towns.
-Buy the Deeds to every shop.
-Get your Drivers to Lv. 99.
-Complete the Driver Affinity Trees.
-Get all Pouch Expanison Kits.
-Defeat as many unique monsters as you can find.
And its not too mandatory, but maybe collect all of the necessary items for fully feeding the Arduran in Torigoth before starting NG+. This will mean you can fully feed him as early as Chapter 2.
Do all of this and you're fully prepared to start NG+ in an optimal state.
Um,
It makes more sense if you reverse it...
These are the basic completion while reaching to the last chapater
-Get to Merc Lv. 5.
-Get Development Lv. 5 in all towns.
-Buy the Deeds to every shop.
-Get your Drivers to Lv. 99.
-Complete the Driver Affinity Trees.
-Get all Pouch Expanison Kits.
-Defeat as many unique monsters as you can find.
I would also add...
- completing every rare Blade's quests, and complete every rare Blade's affinity chart.
So yeah, technically you should just ignore those regular quest to be exact.
and then once you reach to the last chapter...
-Get all Rare Blades so pulling for the NG+ exclusive Blades is easier. (This also includes completing those rare Blade obtain quest, obviously...)
-Get 99 of every core type after that so you can potentially get all of the randomly pulled NG+ Blades early on.
Actually... you can just sell the commons and keep the rare and legendary core crystals
-Get your favorite Blades to S+ Trust.
Also it seems that once you fed the Ardun to 99 and defeated it... once you start NG+, you can still re-feed to Ardun...
But it is somewhat pointless since the tombstone was actually there...