The important thing is that the width is HALF the width that you want your finished circle to be.
For this 6 inch diameter circle, I cut mine 3 inches wide by 12 inches long.
then glue them together to make one long piece, making sure that you keep the folds going up/down/up/down.
Glue the ends together, making a circle (still keeping the up/down pattern),
then smoosh it flat. Put a dab of hot glue in the middle and squish it together, holding it a few seconds until it dries.
I also hot glue a piece of paper on to the back in the middle for reinforcement to keep it from popping back up.
To cover up the middle (which you don't have to do - you can see in the first photo that my garland circles are left plain), I cut a little robot guy outta some other paper,
You can get all fancy and layer it up with more circles and buttons or whatever else you can find lurking on your messy craft table (Kit Kat wrappers, anyone?),
or go country with a decorative BRAD and some PAISLEY. Yee haw.