You'll want wisdom for dialogues and constitution for combat (unless you want to play a wimp hiding behind party members, in this case start with 9 con and never raise it). The rest is optional. I started with 18 wis, 14 con, 16 str and raised str to 18 at the next 2 level ups. If you feel vulnerable raise con, if you feel powerful enough raise another stat.

When you get down to the mortuary ground floor it can get hard if you don't have 11+ dex (for snapping necks) or 12+ cha for convincing the 2 dustmen guards which can't be convinced using a wis based dialogue option, but you can simply kill just those 2 guards, get killed and go down again and explore the level peacefully.