In any previous MMO I've played, I've generally avoided buying things from the auction house. It tends to be cheaper and more fun to acquire whatever it is I want through gameplay myself. It's also a piece of advice that's frequently given to new MMO players: avoid the auction house, it will just drain you of money.
Recently, I'm starting to think that this piece of advice might not actually apply to Neverwinter. My painful quest for an item required to unlock the next boon from the Tyranny of Dragons campaign ended with me realising that it didn't bind on pick-up and that I could actually find it for a very reasonable price on the auction house.
Likewise, my latest alt is once again gaining levels way too quickly purely from invoking, which means that her gear has fallen far behind every time I want to take her out to quest again. Yet on the auction house you can buy levelling blues for pretty much any class and gear slot for two-digit amounts! (Astral diamonds are precious, but even a low level character will gain three-digit amounts of them purely from invoking every day, so this is incredibly cheap.) It's really a much better use of your time to spend that minuscule amount than to struggle with every combat while you wait for an appropriate drop or quest reward.