There is the neverwinter wiki where you can find the sets of any class(though some has inaccurate stats and others missing the drop dungeon). The best way to see if a set is T1 or T2 is to look for the SET2 BONUS. T1 items give +400 while T2 give +450
if you click the icon next to the AH(top of your screen) you'll see three categories,bottorm left is the dungeon.As dkcandy tipped you must first unlock it