Gillionaire can be found either from Rikku's Ultimate Weapon or from 30 Designer Wallets, 60 of which can be gotten from getting one of every monster from the Omega Ruins. I highly recommend the first one however, since not only does it give Rikku her best weapon but Gillionaire need only be placed on one character in your active party. Having three people with Gillionaire <> three times as much Gil.

As for Break HP Limit you need thirty Wings to Tommorow. These can either be bribed from Malboros/Great Malboros, won from Shinyru or by winning the "circular" chocobo race and opening three chests on the way down (30).