@HogwartsIt
Contego
Defendo
Protego
Impedimenta
Periculum
Vermillious
Verdmillious
Stupefy them.
Swinging them around until they are dizzy and throwing them as far as you can.
Use a Jarvey to hunt the gnomes.
Lure them out of the ground and trap them before levitating them somewhere else.
Jinx
Charm
Hex
Spell
Wait!
Here's an interesting quiz for you.