I second the mention of needing rulers, straight and circles. You might want to look at DeLoa's Circle Buster rulers:
http://www.deloasquiltshop.com/deloa...clebuster.html
Rather than a complete circle, they have an innie and outie half circle of the same diameter on one ruler. You normally hold the ruler in one hand and guide the machine with the other. If you're not ambidextrous, then you need to be a contortionist! Not with these rulers, however.