The most complex machine in the instructions. Incidentally, my father got an erector set for Xmas one year from my grandmother. He had to wait until the next day to use it because my grandfather and great uncle were too busy playing with it.
whewwww I almost read that incorrectly...ahummmm...some cool design for Christmas....I'm sure
I'd have to start with the easiest thing in the instructions included with the set and work up from there. I've never been very mechanically inclined.