Pick Merc
Pick wood sticks (timber fury)
Pick hunchback, classic

Pick everything that increases sacred dmg, casting speed and range.
Take some evasion if you cant get your range up high enough, fast enough.

Around round 10, you shouldn't need to buy anything anymore, unless you want the boss to be easier.
THE BOSS IS NEVER AFK.

Luck is the best stat among the other 3, rep being the 2nd. Income wont rly help and prospecting is seriously a joke.
Keep your regen at least 0 unless your going for vampirism. It probably wont kill you with less but, taking dmg is annoying.
Moving around and collecting gold will net you more but, also annoying.
Actually avoiding attacks and getting gold, you can easily beat all difficulties with merc... or saint.