I hate to admit it, but I suck at DoD. I've never made it past the third floor, and only ever made it that far with a viking/barbarian/smith build. I refuse to play anything short of GR permadeth on account of me not wanting to die a virgin, so how can I drive a mage through one end of this game and out the other?
Take either Golemancy or Promethean and get a pet as quickly as possible. The mustache golem or wyrmling can tank the first few floors easily. Psionics is another great skill set, the 2nd level (psychokinetic shove) is basically a game winner. It is a 3x3 spell with knockback that you can get down to 1mp within a few levels. Use this to keep enemies at bay. Blood magic and ley walker are good skills for passive mana regen. Taking alchemy and getting it to level two will give you access to 2x mana potions and the best fruit liquors to keep you good and mana filled (drunk). Once you get a good setup running (basically, just try to survive until you get your first pet), focus on building up your mana regen stat until you get to 1mp/1-2 steps. By then you're basically invincible and will only die if you're careless. The big challenge is surviving the first character level or two.
Promethean is still king, but Psi is good as well as you can spam force push and get kills quickly. Always take blood magic (magical training is decent as well) and a teleport skill, like Dodge or Mathemagic.
Promethean+Mathemagics+Bloodmagic makes a great combo. Also Necronomiconomics can be good, but is tough in the beginning (and it has a steeper learning curve than other skill sets). Both Astrology and Viking Magic are good supplements for a mage-warrior type build (adding in Vampirism is cool as well, but you may want either alchemy or fungal arts to supplement the healing you may need).
OK, here's the breakdown. Staves Dual Wield Alchemy Promethean Viking Wizardry Psionics Your choice of Burglary, Archaeology, or Magic Training The theory goes like this: You beat-stick your way to Wyrmling using dual staves with Lightning enhancements, then you hide behind your Wyrmling while you max out Alchemy. Once that's done, you build yourself a Fruitful Staff and a Jingly Jangly Staff of Crystals, and start collecting fruit to turn into booze through your Alchemy. You booze up constantly, keeping the mana spigot turned on while leveling up first Psionics to Crystal Healing, then Viking Wizardry to Hand of Belamwyr or whatever it is (maybe snag another level of Promethian for zoo-clearing-Fireball purposes first?) Make lots of Health, Regeneration, Mana, Invisibility, and Spatial Distortion potions for emergency use, and kick ass all the way down. Lighting Dredmor up with Psionic Shoves into a corner while your Wyrmling eats him is the cheesy way to win -- but it's also thoroughly effective.
First two attempts died on floor one, and the third lasted until I stepped on fire after a tough battle. I made the mistake of taking and leveling Ley Walker before alchemy or psionics, although i did stick to getting wyrmling first. Oh yes, my build was: Promethian Dual wielding Psionics Ley walker Staves Alchemy Viking
For one among many of my wizard iterations, I was using unarmed combat instead of staves, and it worked pretty well. Being able to use a crystal ball and a shield (or dual wielding shields) is very nice, and on a plus side, using the Throwing Buffalo Technique (kicks an enemy back 3 squares) and Dragon's Breath/Animate Blade Being over and over can go a long way for the first couple floors. Here's what I'm thinking for my next build, though: Staves Perception Alchemy Formal Magic Training Ley Walker or Fleshsmithing Golemancy (my personal favorite) Promethean
About Ley Walker: just remember that the spell Thaumaturgic Tap in Leylines is broken. It checks for your character's resistance, and if it is high enough, you don't gain anything from casting the beneficial spell.
must-have for all heavy mage builds: Promethean Magic - all spells are useful and incredibly strong. each skill gives you fire resistance too. Blood Mage - almost unlimited mana (especially when killing a zoo) Magic Training - to make your spells more effective Alchemy - not only useful for potions, but also to craft equipment. also supports your magic powers Perception - a good eyesight is your life insurance. if you kill your opponents from far away, they cannot attack you. still 2 vacant spots i don´t like Golemancy - the wyrmling from promethean magic is good enough. a good mage can wipe out everything without getting in melee range - there is no need for staves/dual wield etc you only get in melee range when you don´t want to waste your mana on weak monsters Ley Walker - together with Blood mage you won´t need any booze. Psionics - Psychokinetic Shove helps you to get artifacts which are surrounded by water Archeology - you don´t need money? send your artifacts to a museum and get XP instead! or change enchantments/use krongs anvil twice etc .. Promethean Magic is the keypoint in this mage builds. the most difficult floor is DL1 - you may die a few times before you get the friendly wyrmling. as soon as you get it, no enemy will attack you again. summon the wyrmling up to DL10 - all monsters will attack the wyrmling first and ignore you.
No singing the praises of Necronomiconomics? The first three levels are tricky without Radiant Aura or other necro resist, though Nightmare Curse is very effective at that stage in the game, and good against named monsters (and doesn't deal Necropain). But then you get Pact of Fleeting Life, and suddenly your wizard is an invincible melee monster (at least for a while). Then you get Eldritch Inhabitation and you never have to worry about named monsters again. Then you get Tenebrous Rift and you can clear monster zoos by sneezing at them (and with Blood Magic that'll also instantly refill all your mana). Necronomiconomics alone, as long as you manage your magic power/necro resist (and Mark of Cthon helps with that), will easily carry you through enough levels to fill out the build with any missing ingredients (Mathemagic for teleportation and single-target damage being my top choice, since escape and lesser destructive magic are all you really lack at this stage, and maybe something for traps).
Mathemagic is a bit useless in the current build because of a bug that negates all Damage Over Time effects if at least one of the effects gets resisted. The teleport is still good.