I'll use most anything that is 50 weight or finer, and comes in large spools - When I find Aurifil on sale somewhere, I'll stock up - also use just a few neutrals. I don't buy small spools at the local chains for anything other than garment sewing when I need a specific color. For quilting, I buy Isacord most of the time, because I have a local source - it comes in a million colors and is not at all expensive at abour $4 for about 1,000 yards. I have only had an issue one time with trying to FMQ with Connecting Threads - kept breaking, might have been just that particular spool, but it has made me shy away from buying it.