It becomes a lot easier to get it on disk 2. On disk 1 there is a very small way to get GP as opposed to Disk 2 where you will be able to get the snow board, submarine, and chocobo racing access. On disk 1 you only have the bike, the arm wrestling and basketball mini games. It costs 10 GP to enter the battle arena and getting the points for Omni-Slash can be harder than expected. Plus I had heard that the guy who can sell you 150 GP in the first gold saucer screen isn't there until disk 2.