Add ons, map packs, etc. You do not want the arcade if your smart. I wish I got the elite(I got the pro), because with the new xbox features you can rent a game and install it onto your harddrive, and with a 120 gb hard drive you can install quite a bit of games. And when you get bored of one, and HD full, just delete it. This would truely save money..
Once you get that, a good starter game for me was GTA IV online. You can go on and on and on playing freeplay online. I have no idea when Skate 2 comes out but, I can play skate 1 for some time myself :)