Obelisk treasure trick never worked for me, but getting a Guinevere at level 15 helped a fair bit (looted the gold dragon in the Temple of the Snake )

I sell (and enchant) everything I get, but Arena awards give me the most cash I find. I'm up to 372,500 for one combat now (with the aid of a Divine Power potion and a few items of power). The money from the Arena goes up faster than the money needed for training, so I always have spare cash. Even training 4 people.

Never realised Armageddon worked on dragons. Thought flying creatures were immune!