To get the Rinoa card you need your ifrit card and fast! Remember who took your Diablos card too? It may be a good idea finding a save point and challenging these two until you snatch your cards back! To get the Rinoa crad you have to loose the Ifrit to him in a card match: so if you want that card, definitely destroy the ones who took your cards!
Back to the subject, there's a man wandering around near the gateway in Deiling, on disk 3 he has the Ultima or Omega weapon card (which it is i can't remember) and he also has the majority of the upper level cards, so if you can wait for a bit then that'll be your prime time to get you some new cards.