I agree with the Red Snappers, but I love the Red-E-Edge side clamps even more (from the same supplier, Renae Haddadin). An extra bobbin case is great, because you may drop and damage the first one and will need a replacement without waiting. Lots of bobbins, thread (but don't buy a ton of any one brand until you know that you and your machine like it), extra needles. I listen to books on tape while I quilt or sew, so a portable CD player was necessary for me. Machine oil with the long flexible plastic spout, canned air, cloths to clean the rails and wheels (I also use alcohol for cleaning them). I use lots of thread socks too. And some sort of storage for the thread cones and half-filled bobbins.
Have fun with your new "toy."