This pin links to Teal & Lime, which has a tutorial for how to make a Christmas tree skirt out of a round tablecloth. This is great, because it's pretty simple but looks nice, and you could even upcycle an older or thrift store tablecloth. I love mine, and really enjoyed having it under our tree this year!
Mine was $10 at Target (it could be cheaper if you caught them on clearance!) and a great fabric and color. It looked lovely under our tree, nestling our gifts.