In the edgeless world, your best best (if you insist on thief) is a straight thug with cheapshot. Knife is good and take your pick of the general thief skills. Don't think there's any value in trying to dabble in other paths with the 30 points you'll have after thug/cheapshot. Knife is one round opener with dam multiplier - it's a lowbie killer as very often you can knife/flee/return/knife very fast. Gouge can be used mid-combat, but it's two rounds, so sucks for flee/return. I would suggest weapon trip and going defender.

But consider that assassin has trance on top of resist, built-in healing instead of necessity of defender (or mad healing if going defender), assassinate (that no thief has), kote/kans/axekick for maledicting anyone into the ground, etc, etc. Your life would be much easier as an assassin IMHO.