The template plastic is fairly cheap, but their are 2 kinds. One can be ironed on and the other can't be. They also make a plastic template cutter that works great.
I have used cardboard and find that the pieces don't always come out the same size. Once you mark around the cardboard it starts getting smaller.
Bacon liners work great, but don't iron on them.
If I'm cutting circles for yo yo, I iron on freezer paper, then take my circle cutter and cut away.
Also, you can buy plex glass and cut your own templates with a small saw if you are real handy.
Have fun.
VP