You have gotten good advice! I second the larger needle and loosening the tension. Jamie Wallen suggests loosening the tension until you have loopies on the back and then tightening a bit at a time till you get your optimum stitch. There is a video on YouTube on this by Jamie. Don't beat yourself up too soon..this long arming stuff is a PROCESS. Everytime you have an issue, and you figure it out, you are learning to trouble shoot for next time. ASK ME HOW I KNOW! lolol That said, my go-to threads are Permacore and OMNI when I want a matte/cotton look (they are not cotton however..) and Glide when I want a shine. You will find the threads that best suit YOU and what you want as you go along. Congrats on your new set up...and happy quilting!