... and then I go back to where you are in the grand scheme of things. Because if you have never been backpacking at all, you don't even know if you will keep going, or be one of those who goes two times a year, or one who quits the job and spends ten months of the year on the trail.

For the first trip or two, I recommend a rental bag, rental tent, rental pack. If you have decided after that to keep backpacking as frequently as possible, buy a really good sleeping bag, a pack that fits, and a really good shelter (most of us end up with a couple of shelters to suit different seasons) - the stuff you will depend on to keep you comfortable and safe. A very good quality down bag like Western Mountaineering or Montbell will last you decades, with proper care.