Do the math.
Starting spells are defined as Te+Fo+MT+Int+3.
Let's say Te+Fo are 5-15, and Int is +3 and MT is 3-10 (seems "average" enough). So the values range from a low below 15 to a high above 35.
So, a true generalist will have 15-20's, a true specialist will have 30-35's (or more).*
(* It's easily possible to get 40+ (even without a Focus) - but that's at the extreme end of the bellcurve and entering diminishing returns.)
An "average" mage (if there is such a thing?) would have their best spells at 25, with some "slop" effects in the 15-20 range.
A mage can get away with pushing their "non-combat" spells to the extreme limit of their casting ability. If no one is trying to kill you, you cast, and if you fail you wait 2 minutes, catch your breath, and try again. Specifically utility, healing and many Intellego spells fall into this category. (Some so called "non-combat" spells need to be cast reliably - these obviously fall outside of this rough rule.)