Hi,
I think that the side discussion of great tool kits for a magus both coming out of gauntlet and at various years past is a good one. The Magi of Hermes book only partially addresses this, because these examples are idiosyncratic; they are useful but they don't quite address the same question of how to create a magus who is generally useful and playable across a wide variety of stories. And powerful too of course because that's why we're here in this thread. I don't believe
I don't believe there is a single great toolkit. The conversation of essential spells have come up numerous times in these forums, and essential spells break out by category of function rather than specific spell. But a toolkit is bigger than this.
It must have essential functions that answer some basic questions. Can I get out of Dodge? Can I lay down the smackdown in combat? Can I do something in a social situation other than get out of Dodge? And more, but these are the basics. A toolkit should help a mongoose control his environment. New paragraph new paragraph
Some of these spells will benefit immensely from laying on the mastery. For example, a plum of fire is great but a pilum of fire that I can cast quietly while tied up at lots of people in a church before anyone reacts is even better. Teleporting back home is a great get out of jail card, but I'd certainly like to put silent and subtle on that, in case I am teleporting from shackles. There's a mastery that suppresses sigil and I suspect that will be helpful on one or two of these spells. New paragraph new paragraph God damn it
So I'd love to see various toolkits for an optimized flawless magic magus coming out of gauntlet, and I think these are particularly interesting because they will reflect different kinds of choices that have to be deeply considered due to the heavy investment involved. And I think that the benefit of pimping out spells with flawless magic is going to be greater rather than lesser. New paragraph
As an aside, which I might have mentioned some time ago on this forums, I think that spell mastery has a cultural impact as well. Pilum of fire might not be the very very best Korean spell a flambeau could learn, but it becomes a lot better when you consider that the house has been writing books about mastering the spell for nearly half a millennium. Many of these books are trash, but quite a few of them are not considering there are probably so many of them. And, of course, Maggie outside the house are well aware that flambeau will pay well for good books about their favorite subject.
The order probably has a few other boutique spells of this kind. Flawless magic doubles the value of all those trackpad high. Okay, all those books. 
If your tool kit runs toward rituals, flawless magic plus cautious magic plus a familiar really helps. Of course, a pure ritual magician or mostly ritual magician might want mercurian magic rather than flawless magic. But the latter is more versatile, if not quite as good for rituals. New paragraph
It's a bit strange to me that I am here advocating flawless magic because while I think it is a powerful virtue it is not one of my personal favorites. But I do notice that when I see a newly gauntleted magus with flawless magic online that is well done, I find myself admiring the cleverness of the player and power of the character, where power means a combination of ability and flexibility. Anyway,
Ken