Farming the Imperfect (Dinosaur monsters) by the third bonfire is by far the easiest way. They have an insanely high drop rate with serpent ring +1 and Symbol of Avarice. Additionally, they also drop titanite slabs and Dragon Scales!

The easiest way to farm these Petrified Dragon Bones is, i believe, is in Dragon Aerie. Yes, you have to burn Bonfire Ascetic every time, but in the first "cave" you go into, there is everytime new Bonfire Ascetic on the first corpse. In first Wyvern nest, on the right side is the first one (dropped from Crystal Lyzard). Two more bones on right side before you enter second Wyvern nest on corpse and one more is dropped from one Crystal Lyzard in the second Wyvern nest. So its 4 Petrified Dragon Bones almost for free.

Using a bonfire astetic on the tower of prayer won't affect the elana fight will it?

I tried the ascetic farm and none of the chests reset

you can also get rare/boss weapons from the crows if you trade

1 is behind locked door next to Straid

There is one on the body on the broken wooden stairs in Iron Keep aswell. At least there was in ng+2 .

Wiki says Dragon Sanctum. It's actually Sanctum City, and the bones are in an iron chest.

You are a scumbag liar.
DO NOT LISTEN TO THIS PERSON.