Grind 10 levels of strength and enable beast mode two handing the dragon greatsword.
Now that Andre is dead, you are free to eat for souls all the boss souls since you need to +10 a weapon for ascension and only Andre can.
The dragon greatsword does respectable damage at +5 and the special R2 is always useful for tight situations (don't forget to buy repair powder).
Alternatively, as everyone has suggested, go fire or chaos if you think you can hold 10 soft humanity.
Now farming dragon scales to upgrade sword is a pain but... you can get 8 of them (all you need to +5 the sword) without killing a single dragon.
Thanks, so I can consume all boss souls since Andre is dead then? How about in NG+, can't I use the souls then if I chose to (when Andre is back)?