What it says on the tin. Obviously, this will depend to some degree on the troupe, but as a general guideline, what spell levels should a magus just out of apprenticeship be able to reach in order to be... I dunno how to describe it. Adequate? Deserving of their status as full-fledged Magi? Capable contenders in Hermetic society?
Really, it's whatever standard you want to use, but what levels of spells/casting total should they be able to manage, in your opinion? (Speaking practically, you might not always want to use your highest level reliable spells, because they'll only have a little left for Penetration, but still the Casting Total is obviously in consideration)
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.)
I strongly suggest magi be able to Penetrate Might 10 with at least one useful spell out of gauntlet. That's probably a level 15-20 spell with a Casting Total of 25, not counting Aura. Usually this will be a spell in their focus area; and is easily achieved with an Arts score of 8 (Te8, Fo8, Foc8) and +1 Stamina, for 25+roll+Penetration. The same logic applies to non-combative magi; be able to reliably cast useful spells without blowing fatigue. The bar is set lower since you don't need Penetration, so level 20-25 spells are better targets for these spells given the same arts.
Shooting for the moon (spells at level 30-35+) right out of gauntlet is possible (and impressive!), but there are a lot of low level spells spread across the arts that are very useful to every magus (Wizard's Sidestep, Eyes of the Cat, Bind Wound) and it's FAR more efficient to learn them during apprenticeship (learning spells from a teacher will save you multiple seasons early on). The XP eaten by the arts and big spells keep you from taking them. The moon-shooters are usually VERY effective against mundane targets, though.
On the other end of things, if you can only manage level 10 spells with 5 points of Penetration, you're still a worthy magus (yay, you can do magic), but you'll struggle vs creatures with Might. Certain concepts can pull it off - such as a magus who has lots of Single Weapon Ability and buffs his Parma hard very early, or someone Finesse focussed. Generalists don't do combat well, but often have a broad base of spells that make them more useful outside of it.
More importantly, perhaps, is to not try to be too esoteric right out of gauntlet with your spells. Choose practical effects with obvious applications, rather than rituals you'll use once a decade.
There isn't going to be a hard and fast answer here. Sure the troupe and saga is going to dictate some of this.
Some of my recent characters who came out of gauntlet did know 35th level spells and really stretched their Arts to get there. One is a Corpus specialist (gauntlet score of 18+3) and knew The Leap of Homecoming, and the other is a weather maga who knew The Incantation of Lightning with +5 penetration due to CS, +3 penetration score and when you count the average die roll she's easily in that +10 penetration range, and every increase of her Creo Art adds +2 to her penetration... She has other spells in the Auram family, and has Bind Wounds. Then I have a generalist magus who was played through apprenticeship,and his maximum level spells are 25th level Aegis and Ritual Communion (Sun duration Wizard's Communion for rituals). He's primarily a generalist because he has Magic Addiction, and 25th level spells are pretty much his max until his Concentration increases, or he spends XP on Imperturbable Casting... He might very well be a specialist in that he has so many spells at his disposal... That's his defining characteristic. He will contrive to cast 10 spells where one will do.
Knowing your bread and butter spells is important, if you intend for them to be cast against creatures with MR, it's highly advisable to have that penetration of close to 10. It's also handy when you're in an adverse aura... I feel as if I'm rambling. Lots of contingencies, and they are tied to the saga and the concept...
The short answer is that it depends upon how broad the magus' specialty is. A starting magus specializing in a single Technique/Form combination can easily achieve casting totals of 30 or better (see the Flambeau template in the book) while those who spread their Arts a bit thinner will have correspondingly reduced casting totals with 15 or 20 being reasonable.
Personally, I try to make sure any magi I play can get at least 15 in one art combination, but that's mostly a matter of personal preference.
You should be asking the parens of each apprentice: What do you think your apprentice needs to know before you present him to the Order as a fledgling yet fully accomplished member of your lineage and tradition?
When creating a magus, I always do the parens also, and on one occasion his parens too (in that case, all the way back to Merinita, who I left ambiguous.) I don't stat any of the parens, but could have. In some cases, my parens writeups become more interesting than the main character himself, which is perhaps how it should be since they've already done stuff and been done to.
BTW, is Hectic Practices a new hedge virtue, even better than mere fast casting?
EDIT: Not always: My ancient, Penultimate Twilight Tremere "The Diedne are Coming" magus didn't get a parens. No one remembers him anyway.
