How much cash does it take for a blessing and are they permanent?

I have been regularly dropping 200-400 silver at the temples, haven't looted any shrines and destroyed No Name's statues but i still can't get a blessing. How much cash is enough?

Thanks.

Dumping a large amount of cash in one go did the trick, although only when i swapped out the leading party member for a Thorwallian and then a warrior.

Not quite what i expected though, i got a couple of general descriptions of the blessing but not sure how they are implented into the gameplay. Anyway, thanks.