In my opinion Conjure Arrow can be skipped because it makes 10 arrows for 450 of mana. Arrows have an attack of 25, at level 13 (when you can buy the spell) you can use spears and shield (with the same attack power) or even throwing stars/knives (30 atk/lighter and with more range) althoug those are more expensive.
Grat Light is useless unless you have a low ambient light activated in graphics.
With conjure explosive arrow at lvl 25 happens something similar at what I wrote before about conjure arrow, even wuth more options.
The last spell I'll put is cancel invisibility because the enemy can turn invisible again and when you buy divine missile or better divine caldera can make the creature visible again (divine caldera costs less mana make the enemy visible and inflicts damage). However it can be a lifesaver in very specific cases but I'd carry some runes instead.
Hope this helps.