Here are some helpful tips from Lehman's 1213 calendar:
Bake cupcakes in ice cream cones.
Whip up your store-bought frosting to make it go further.
But I'm not sure if storing your sheets in the matching pillow case (to keep them from being separated) will work. I've never tried that, though I've read about it before. Stuffing them in a pillowcase would not be easy, and I wouldn't want to put pressure on the pillowcase material. Let me know if anyone tries it.