don't use serger thread on long arms--serger thread is not as strong, it's made to be used with several threads to create the seam. Long arm thread is made to roll out 1200 stitches "lickity-split". I prefer all Superior threads and also Glide by Fil-Tec; but also YLI and Signal, Marathon, etc. Just make sure they are not their serger or embroidery machine threads.
If you are asking about the fabrics for backing (since you mentioned using pre-cuts), I like Moda's muslin which is very soft and not too sheer.