I'm always using Energy Pulse and Ball Lightning for combat, Ball Ligntning for resource gathering, and Ride the Lightning for mobility. I have every spell unlocked and many spells have no use for me, obviously the day/night spells will become useful once the game has grown a bit fatter but I never seem to teleport, all the lighting spells I ignore because they are not emit light scrolls, which make every other source of light obselete, I havent really wanted to pick up scenery yet but I might do once there is more variety out there and using the scenery for defence never seems worth the effort.
I ignore the low mama attack spells for the same reasons as above, low level Energy Pulse and Ball Lighning do the job better, and Death Creep and Launch Meteor cost too much mana for what you get.
Douse Spawn might get used in a boss fight but I havnent needed to use it in one yet, and I just run past the one's outside, I dont use Death Touch to kill spawn points for the same reason.
And lastly I dont use Fire Touch or Death Touch for mining because Energy pulse is already avalible and works from a distance, and I often run through whole wooded area's firing Energy Pulse and single handedly harvesting entire forests to use in my settlements, without once considering stopping and doing it one tree at a time for the hell of it.
Well thats my use of the spells so far, I regularly use 3 spells out of all of them and thats it, if there was element resistance based on what gem the spellgem is made out of that could add to the combat spells a lot and put them all on the table as options and make me prepare more before heading out to fight.