Final Fantasy XIII Platinum Question?

Ok, this may seem a bit unorthodox but I just finished all the missions except the ones that unlock the Long Gui, I have a mastered crystarium and all the other trophies, except Long Gui, Treasure Hunter and defeat all missions. Should I finish all the missions and 5 star them now, or farm the oretoises for whatever? If it's the latter could you tell me what drops what, and when I have enough of said item to start farming Long Gui? Thank you.

If you've finished maxing out your character then there's no reason not to unlock the long guis (or whatever they're called). I did it before I was even close to maxing out and could kill them, not easily but I could do it. They drop platinum ignots (I believe are called) which sell for a lot. You need them for treasure hunter as well, so you might as well just start now.

Yes if you ask me, since the lone adamantoise in the courtyard is the fastest ingot farming spot anyways.

and the shaolong guis are the only monster in the game that drops Dark MAtter