Oh my what a question....I have made many many king sized quilts and mine were basically 120X122 (really large) as I preferred a certain look on my bed. For a new quilter this could prove to be very daunting. I would personally start with a throw or twin size to build my confidence and reap the rewards sooner. It takes a long time to make a king size and you might become frustrated just at the sheer size of it. Once you are confident you can then start making those king sized quilts for your grandchildren. Whatever you decide to do just take your time and enjoy the process!