Mostly as it pertains to Hermetic Magi.
I'm going to be SGing a saga (none of us have played ArM5 before, so one of the newbs had to), and after poring over the example options presented in the book, we all unanimously decided that the most interesting starting place for the saga would be with the Magi as new recruits to a Winter covenant that has one Maga trying to kick the entire covenant out of decline by bringing in new blood. It's also going to be one of those covenants with a bunch of places nobody's set foot in for years and there will probably be a lot of interaction with mundanes and yadda yadda, but that's all unimportant to my current question.
There will be several older Magi in the covenant itself, but I can safely ignore most of them because despite being old and powerful they're also extremely reclusive, self-absorbed, and somewhat cowardly. However, I do want to make stats for the Maga leading the whole "get out of Winter" operation, since she's important and I don't know how involved she'll end up getting yet... And more importantly, I was hoping to have there be a major background antagonist group who the players might get more involved with as time goes on and they get stronger. The group would be composed of some older Magi who had defected from the Order of Hermes and who now have some interest in the player covenant's hidden resources.
... And, of course, as a general SG'ing tool, I probably want to be able to guesstimate my players' growth rate so I can present challenges in advance and have some semblence of an idea how long it will be before they can accomplish it, and while that will work on an individual basis I figure having rough guidelines can't hurt.
Given all that, I'd really appreciate aforementioned general guidelines. In your opinion and your experiences, what standards should Magi of any given ages be able to muster? Casting totals for specialists? Magic Resistance to be penetrated by main spells? Non-spell skills? That sort of thing. Obviously there won't be a hard and fast guideline, but I don't want to accidentally overshoot in areas while undershooting to crippling degrees in others. (Key word being accidentally, of course; nothing wrong with characters flawed in interesting ways as long as it's happening on purpose)
Thanks in advance for any help!