Vampire is probably the easiest. Recommended preps:
Really Big Sword or Badge
I recommend the RBS version. There's no longer any pressure to find GETINDERE or BYCEPS, and the slow floor effect just bounces off of you. Your life steal is based on damage actually dealt, so resistance piercing ends up being much more important than normal.
EDIT: Got my wires crossed and included two locker items
The most important thing to find on the ground floor are suitable high level monsters to use as a blood bank. Meatmen are ideal, dragons are tolerable, goo blobs are mediocre because their resistence cuts into your life steal, everything else is either a bloodlesss zombie or is too fragile to last until the end.
HALPMEH is not needed , but is tremendously useful. You probably need either HALPMEH or a good pair of blood cattle to win consistently.