First draw a circel on a piece of paper, the size you want the wreath to be.
I've collected branches from our back yard black walnut tree. I've cut them in 3 inch pieces. Then glue the sticks together with a hot glue gun. Some bigger and thicker pieces you have to use at the bottom to make it more stabil. Make the wreath as thick as you want. The only thing you have to make sure is to stick the pieces on at least 2 places for more stability.
Have fun with your new wreath!