I use the cheap thread from Thread Art. It's cotton, 40 weight, 3 ply. It comes in 2500 meter cones for less than $6. I use white, it comes in many other colors. This thread is not the highest quality ( has lint and the occasional knot) but I use lots, the price is right and it is strong. My Tin Lizzie likes it, I use the same in the top and bobbin.
There are many better brands of thread that cause less lint, I have to clean the bobbin area with each new bibbin. Every quilter (and their machine) has their favorite thread, my choice is cheap, strong and works for me.