You start with 0% crit so to make spells crit you are pretty much forced to:
1) Play human or Fane
2) Get crit on gear
3) Maybe invest some in the crit ability (wits?)
I have no idea if crit on your staff is global crit or local crit however, I haven't tested that yet. But I assume the crit multi on a staff only applies to your melee attacks with crits even /w the spellcrit talent (can a Larian employee confirm?)
