Hi there and welcome to the board! We are glad you found us, you will love it here!
About the thread, I can give you my opinion and you can take it for what it's worth. I am not an expert but, did own a quilt store for 3 years and a Pfaff dealership so most of my opinions and knowledge come from those experiences.
First of all, when doing your peicing of quilts, you need to use 100% cotton thread. It won't cut the fabric and will wear better over the generations. It is also safer for infants and children. That being said, there are times you will use Polyester (embroidery) or specialty threads for embellishment or quilting. But, generally stick with 100% cotton for piecing.
I personally use Gutermann, Sulky or Mettler. They are all of higher quality. They are also wound correctly to come off the spool as to not tangle or snag in your machine. They have a smoother finish. Some machines are fussy and when you use a lower quality thread, the machine will not work as well. Sounds weird, but true. We had customers bring in their machines for repair because it was not stitching properly often. Most of the time when we switched to quality thread and made no adjustments, the machine stitched much better.
Hope this helps some. I am sure there are others out there who can give more insight as well!
Again, welcome!