I have basic gear that was meant for camping, but not backpacking (think Academy or Wal-Mart tent, sleeping bag, etc.). I am looking to upgrade for backpacking. I have a decent backpack and footwear. What would be the best use of $500 to upgrade.

I am thinking a light sleeping bag, sleeping pad, and a good tent, but I am looking for options I might be missing. What other misc gear might I need?

Thanks for the help.