To start you'll need some card stock. Colored card stock is fun because it can add a little pop of something if you've got kids helping and the paper doesn't get 100% covered.
Card Stock Paper, Assorted Pastel
For keeping the paper in place while you make your tree shape.
Scotch Transparent Tape
This could be cute as it's own tree, or as an addition to another made with solid color ribbon.
Offray Ribbon, White 5/8 inch Sheer Ribbon, 9 feet