what is the best way to farm gil in ff13?

[cloud1161]

i have all the trophies for this game except treasure hunter.  ive been farming long guis and shaolong guis for about 5 hours (in game time, not straight through) and all ive gotten was one platinum ingot, a dark matter, and a trapezohedron.  other than this strategy, the only one i know of is digging with the chocobo, but that doesnt seem like it will be too effective either.

 

EDIT: i do have the collectors and connoseiurs catalog equipped.