Also if you get the message Im sorry but at this point the oracle cannot do anything for you... the voices are silent... Do two things
1.) Check to make sure you didn't get a reward in the past 24 hrs. If you did stop there.
2.) IF YOU HAVEN"T GOTTEN A REWARD IN THE PAST 24 HOURS try donating another 5 mil gold. Everytime I have done this with the exception of 1 it has worked (tested it around 10 time now) Always recieved the prize of 130 mil gold to 220 gold.
Also different strategy for when you have more gold:
Donate 15 mil 3-5 times and you get a reward... this is just an alternative way to donate if you have more geld. I have also found that donating 5 mil the same way works, as does 10 mil, pretty much any even sum OVER 5 mil works... 5 mil normally gives gold, 15 mil. give a hero enchantment or spell level increase, and 10 mil gives what ever it wants