Thrift store.
Added bonus--they often have partial rolls, so you can buy just enough for what you need. I spent $0.23 on wrapping for a baby shower gift, using every bit of it. I didn't have to store a partial roll for ages until the next specialized event. Normally I buy a big roll of plain, one color wrap that works for multiple holidays (red works for xmas, birthdays, valentines day, etc.)