First off, cut out a triangle, any size you would like :) then measure a smaller triangle inside, and draw it on with a pen. This will be used as your template.
Next, grab your template and pin it on, it's okay to do this through the cardboard, it makes it easier to cut out the fabric :)
Now cut away, keeping the fabric firm, so that all the triangles end up the same size :)...
Once you have done one, repeat until you have enough to fill up the length of your ribbon.
Once you have cut out all your triangles, give them an iron :)
Lay out all your triangles, and run your ribbon across the top, like so..
After laid out, put ribbon on top...
Next step, is to pin the the ribbon and fabric together, ready for the sewing machine.
Get to the sewing machine and sew a straight line across the top of your pinned together bunting line, using a straight stitch, or if you wanted, a cross stitch.
Once you have done that step, then hang them up where you please!
Easy and cheap bunting! Walla :)