Tacky Holiday Sweater

I'm so excited because I'm going to a tacky holiday sweater party! I've never been to one and don't have a sweater just sitting around for the occasion. So the question is, do I buy a sweater from Goodwill or Ebay or do I make an outfit?

Funnily enough I've dressed up as a Christmas tree for Halloween before and it was a huge hit. I could always recreate this costume.

Or I could go with the bow tree skirt and a tricked out headband.

Or maybe go with the little kid art project route.

Have you ever been to a Tacky Sweater Party? Any suggestions?