I've invested in everything but Res, Attunement, and Faith, which is the problem. I've got dex enough to wield the Silver Knight Sword.Keep in mind that the Furysword requires Demon Titanite to be upgraded, which is harder to acquire than Twinkling. (can't be bought and must be farmed from the Titanite Demon's, most of which do not respawn).
Also the Furysword is a Dex weapon, I don't know if you have invested in that.
I've also got enough Demon Titanite for at least one special-soul weapon to max out.
Today I just did grinding. 80,000 souls in the painted world of Ariamis to grab 10 pieces of Twinkling Titanite, then more grinding to buy Large Titanite Shards to max out the Scimitar and convert it.
Then I went down to Darkroot Basin because I'd forgotten to pick up the Grass Crest Shield after killing the knight down there, discovered the tunnel to New Londo Ruins.
-max Quelaag's sword
-upgrade the iron armor a bit.
-maybe upgrade Grass Crest Shield a little for more magic def
Then I think I'll be ready.