I like to use the smallest needle size that makes the proper stitch with the thread I'm using.
I usually use 50wt or 60wt thread (or a polyester equivalent) for piecing and the needles that work best with those sizes is probably going to be a 10, 11 or 12.
I use a variety of threads for quilting - if I'm using Bottom Line in the needle, I use a size 9 or 10 needle for quilting. If I'm using a 40wt thread (or the poly equivalent) I use a 12 or 14 needle. If I'm using a 30wt thread or larger, I use a 14 or 16 needle - or even larger, just depending upon what it takes to form nice stitches with the combination of fabrics and batt and thread.
I buy ordinary 15x1 sharp needles by the hundred on eBay for $12-15 per hundred - Organ and Orange brands are both very low-priced but high quality.
If I need specialty needles like twins or wings or topstitching, I need to go to one of the more expensive brands, like Schmetz or Klasse'.
I use any kind of thread that has the color and effect that I want. Sometimes the thread is the same in the needle and bobbin and sometimes, the thread in the bobbin is wildly different from the thread in the needle.
Set your bobbin tension for the thread in your bobbin, find the needle size that works with the thread you want in the needle and balance the needle tension with the bobbin tension. It will all be second nature to you before you know it. :)