yes u can go to the chocobo lagoon and get choc graphs there and get upgraded too

as for master theif u have to buy the Thief Gloves for 25000 gil at the Treno auction (on like disc 3) or go to a place called Daguerro, which is only accessible by airship or flying chocobo, and sythesize it there for 50000 gil

Master Theif allows u to steal better items