so, Mage, what will you do with all those gems?

[Zooko]

I've noticed that my mages will use gems in order to cast a spell that I've scripted for them but which is too high-level for them.

I've heard that they will also use gems in order to avoid being fatigued-out.

Will they use gems in order to get better results from a spell, like extra damage?

Will they use gems in order to get better penetration against enemy magic resistance?

I'm thinking of trying a spell which would require lots of extra gems poured into it in order to overcome enemy magic resistance. Is there any chance my mage will do the right thing?

[Chazar]

AFAIK, the maximum number of extra gems is limited by the inital skill, ie. a 2lvl Air mage can only spend 2 additional gems. Furthermore I recall that only one gem adds to the skill, while all remaining only lower fatigue (as if raising skill).
I do not find the thread where this is posted, but it should be (and probably is not) in the manual and it probably is (or probably will be) written within liga's manual addenda.

PS: It's actually within the manual: see 6.4.7! I am positively surprised!

[Ironhawk]

I dont believe that using gems confers additional penetration powers. The only thing that would effect that is the +1 level boost from the first gem you use. If that increased your base level over the spell enough you could get the normal penetration bonus