Okay so, this is pretty much near the end of the game. Once you obtain the kings ring, its time to take your ass up to the Dragon shrine and obtain the ashen mist heart. The mist heart is used for being able to enter the memory of the giants you see around the game. The one that's best for farming is the Memory of jeigh this memory contains The last giant boss, the best farming place in the whole game. this boss is a pushover and easy as shit.
Major tip to endlessly grinding this for souls, when you enter this memory after you go to through the mist gate, go to the left and up the stair there will be a bonfire ascetic this is the key to never losing a ascetic and having infinite numbers of resets.
Tips fighting this boss. ALWAYS stay to the outer left side of his foot at the centre basically, he will never be able to hit you, he has a stomp move thats the move you have to doge but its so slow and easy to see you will be dodging with flying colours. rinse and repeat the boss will die in no time flat, once you beat him return to the nearest bonfire which is 2 feet away and use a bonfire astetic which resets the boss (warning this puts the boss into NG+ mode, meaning its harder more health, and mor importantly more souls. As far as I know the game goes up to NG+8 so keep that in mind when you reset a boss. It will carry over to the next playthrough.) then go back into the memory get the ascetic beat the boss and the same again.
Tip: just below the Giant memory thing is a some twinkle titanite so this is great place for endless amounts of that if you need it too, ascetic reset items so you got endless amounts now
At New Game +8.
and Covetous silver serpent ring + 2 ( increases souls)
and
Tseldora amour Set (increases souls) The easiest way to get this amour set is killing the merchant in majula on the left shop as he gives the set. only kill the npcs if you are starting a new game + so they will return to life.
You will be obtaining 470k souls each time the boss is killed. I can kill the boss in under 2 or 3 mintutes. its easy and fast.
another note, every time you kill the boss you will obtain his soul which is another 25k souls if used I believe so yeah. best soul farming so far in this game.