Blow up balloons and with a needle and thick thread thread them together to make a balloon garland. This is very cheap and a great way to add a lot of color to a party. You can use thread but would be more secure if you used embroidery thread. Mix and match colors for your theme to go with the colors of a school for graduation or just go random for a birthday party. This can be something done at the last minute as well as you can get everything you need and have it ready to go.