In this video i install a US Energy garage door insulating kit. This is probably one of the least expensive kits available.
https://www.amazon.ca/gp/product/B01M...
*NOTE*
Although this is a very light product. If you have an electric garage door opener, You may have to have a qualified technician adjust your door spring. This is a quick and easy job but should not be attempted by the home handy man. The spring can be very dangerous. In my case the door was still balanced so no spring adjustment was needed.