I get a bunch of peridots, plus the occasional sapphire or opal, using the dragon hoard enchantment(s) in my utility slots. Not sure if this is what you are looking for, bur I hoard them then wait for a double refinement period to use them (when I'm patient...). The marks of potency elude me, which is why I am cruising…
I found that if you do "I am stuck" and then "defeat me" it resets the drake placement without having to re-do the whole dungeon. Very annoying though.