Which is the most viable by type and location to farm for maximum efficiency?

Best for starting to farm gear/runes are probably blizzard, hydra, fireball, nova, lightning, orb.

You need to tailor your farming locations to your build. For example a nova sorc isn't going to run bosses or travincal like a blizzard sorc but they can run pindle/eldritch/shenk, keys and arcane sanctuary.