I have several different machines but for the most part I only use one thread; Aurifil. It is only 2ply, 50wt but very strong and very low lint to mess up your machine. For piecing I normally use either a natural or beige or tan color no matter what the fabric is. That's the nice thing about piecing; you don't have to match the thread to the fabric like you do when making clothes. I also like the Aurifil when doing hand applique; it hides in the fabric very well.