Spidey : you're wrong there.
The key is to donate twice, however you donate the first time.
Once I gave 60.000 + and the gods were still not pleased.
With a first donation of 3000 and a second one of 1500 or 2000 that will work.
I also believe that the total amount you need to donate has to do with the number of turn you pray.
while praying only 2 turns, I had to donate 3 times (total around 8000 gp)
while prying 4 turns, I have to give only the aforementionned 3000 + 2000.
In short, dont hesitate to donate less, but more than once.