I tend to use a buncha different spells myself.
I use a controller for this game though.
Let's see.... my main spells are:
Energy Orb: my main attack spell
Energy Slice: absolutely amazing against things like dragons, fairies, and those giant green amoebas
Miasma Whip: great against robots, things like bats, and it's also used to break background objects
Fire Shield: helps quite alot in certain situations. Good against those summoned fireballs, among other things.
Flash of Light: obvious use.
Light Snake: obvious.
Summon Rhino: great summon spell, very very useful against ground foes, particularly while I'm already dealing with air attackers.
Creeping Death: used correctly this is very powerful. The slowness of the projectile is useful as well.
Tidal Pulse: Well I WOULD use this one alot if it wasnt nigh-impossible to upgrade without swamps available.
Splashback: Obvious use.
That's pretty much my current setup; on continent 2 in my game, playing on Hero.