You can always open 3 chests at the chocobo race under Remiem temple and you get 30x Wing to Discovery. Getting loads of gil is very easy, just have the gillionaire on and fight alot in Omega Ruins and every time you fight the lizard and the chest steal from the chest and either you get a mega potion or something like that or you get 100,000 gil. That is if you kill the Mimic.