I get gift cards at Giant Eagle, which offers fuel discounts for purchases. The highest they have is $100 though. I felt bad for the TM at Portofino Bay because in order to redeem GC, they have to call a number, input the card #, and get a code back which they then have to enter into the system. I had many GC and she was having some issues with the system. I think paying at CBBR was much smoother, perhaps they have a newer system?
Disney has an online system where I can combine my GC into a few larger ones, which I do before my trips there.