Weak character generally don't survive SMC/UD runs. You need to be very careful and have a good amount of luck. I would normally just open the SMC, if that, then come back at much higher level.
For the SMC itself, it helps if the stairs start really close together. For low PV characters, you may as well true berserk everything so that you at least have enough damage to 1-hit most monsters. You may want to pick up PV/speed/Heir with your starting talents for an extra boost in the early game. Also, play drakeling for acid breath.
Hoping to win with every class, doomed. Archer, Barbarian, Bard, Beastfighter, Druid, Elementalist, Farmer, Fighter, Monk, and ULE Priest down.