You have to purchase a ruler foot for your type of machine. Some of our machines are high shank, some are low shank. A dealer or foot seller can help you with the right one. Rulers are for sale everywhere, just make sure you are getting the ones that work with your ruler foot.....some rulers are 1/8th inches and others are 1/4 inches thick. You can free motion ruler work with cotton or polyester thread. The contrast or no contrast color of your thread is your decision. If you want your stitches to show, use a different color from your fabric.Do a practice sandwich first. Bobbin thread and top thread work well together is the same weight, although some quilters like a lesser weight on the bobbin. Also always pull your bobbin thread to the top before you start FMQ, this eliminates nests and thread jams.