Im up to 17.1 million souls now. I would farm the forest npc people all day while listening to Zed's Dead. And a few times my friend would let me sit behind the scenes and kill people in the forest. (Doing that gave me about 9 mil souls on it's own)
With all of the farming I boosted from level 77 to level 193 and on made me able to buy the magics I wanted.. My big fail though is that I still can't use Soul Spear.
I know there's people that beat the game without even leveling but I feel this is probably as good as it gets for me right now in this game.