Efficient playstyles shift over time based on a "meta", like in competitive games. Strategies will come to be common place, especially for casters. Don't let those strategies dictate how to play your character, but recognize you'll have to prove your worth if you do.
Example, for a while wizards will do little but buff warriors, then clerics will be self buffing front liners, then nukes and crowd control will come into prominence. Pick a class and pick the spells you consider fun and appropriate for your character as well as efficient, not just the latter.