If there's one thing you should read before jumping into this game its Beamup's
Combat Mechanics Guide over at GameFAQs.
Main thing to take away from it is to just focus on having 3 weapon types edged/blunt/piercing then to just enhance them further with spells/gems for the different situations, this is by far the most effective strategy to damaging enemies and the least tedious. Going the 6 different weapons for each enemy class route is not optimal and here's why, not all undead are weak vs blunt weapons so banking all this time training your blunt type undead killer will go to waste.
For example:
Skeleton "Undead" resistance to EDG +2 / PRC +9 / BLN -16 , here blunt is good as its weakest most to blunt and strongest to piercing types.
Mummy "Undead" resistance to EDG -5 / PRC +5 / BLN +8 , here blunt is the worst you could use and edged types the best.
Ghast "Undead" resistance to EDG +8 / PRC 0 / BLN +23 , again blunt is terrible here and piercing is the way to go.
Also if you're thinking that training your blunt so its +100 to undead, and that it would still be better that way, is wrong and terribly inefficient, there's actually very little difference gained from it, its about the difference of say -25 to a weapon type, like the Ghast example above, +100 blunt weapon vs +4 piercing and the piercing would probably be more effective or at least close to the same.
Anyway hope some of that made sense, seriously check out that guide its great and will explain things better then me. Oh and enjoy this kick ass game.