water, lightning, ooze, earth, fire, frost, air

Lightning, fire and ooze are the super duper must haves, lightning for a terrain independant one round damage spell that packs good punch, ooze for quicksand, and fire for nova (I will personally drop any voker who isn't doing unspeaks after 35 in ~.03 seconds ymmv) and shield of flames (never leave home without shield of flames)

After that, it becomes matter of choice really, I can outline the reasons why you want the other paths, and in order of importance I'd personally pick them

Earth: Earthshield negates dirt kick, shield of earth gives resist blunt (good for solo ranking stormies and what not), and makes it so so much easier to get stoneform

Frost: Iceneedles ftw for sure, frostshield is handy vs. some mobs but otherwise not super necessary

Air: Improved invis is super own, buffet again is ok in some situations but not too widely usefull, vortex is fun but its utility depends a lot on your cabal of choice, the most usefull thing airshield since mob gas blasts are a major pain in the ass

Water: utterly useless (hint: if cranial is causing you trouble, you are doing something very wrong)

Personally I'd pick all but water, if you really want to go 5 paths, then you can drop air too, but it's going to be a pain in the ass when your group gets gas blasted