The issue with even that build Kot is... well...
If your not two hand casting, your wasting a spell. It is the only way to go from underpowered magic to "decent".
As for which kind of magic to focus on... Electric is resisted by the least and is hit scan. Though I focused on all three:
Ice being the worst because most enemies in the game are immune or resistant to it, and it isn't always obvious that an opponent will be immune. With only one enemy being weak to it (as I believe even fire dragons are either resistant or not weak). There are huge swaths of enemies immune to it and it isn't because of the setting. All Machines are immune, all undead are resistant, vampires are immune, half of all dragons are resistant, Most guards and some NPCs are resistant, quite a few animals are resistant, and incorporeal enemies are immune. (In fact... I think there is a shorter list of enemies who aren't immune or resistant to Ice... then there are enemies who take full damage or are weak to it)
Where Lightning the only enemy who has any sort of resistance... is immune to it and is a rare enemy you might fight once or twice in your entire run. Though no one is really weak to it.
Fire is resisted by a few enemies, two are weak. and only one rare enemy is immune.