[Marcus]

Your build is a perfectly reasonable build for an experienced player, my last mage, a whiz ganger, concept ran magic 5, and was setup very similarly to that. Absolutes are naturally absolutely wrong, but structure helps those who are new to system that can be as fluid as SR Magic. This is especially true in 5th, under RAW it's possible to have what basically amounts to 3 different versions of the same spell, between Spellcasting, Group Spellcasting, and Alchemy. So giving examples is the best way to guide, and avoid such issues.

I think the discussion got a little out of control, which is of course always a risk, and of course it is just another argument on the internet as you say. But I think there is benefit to the conversation, thus this post. What I am try to suggest is that as a board we should try to work together where possible to help a newbie like the OP. Which over all is exactly what we did, which is great, but something a little more cohesive would likely be more effective. The first two posts attempted to get more info out of the OP, then ZB put a solid build, and asked the OP to flush it. All of that seems like a solid beginning to me. Things begin to unfocused from there, I'll be the first to agree that neither of my posts did anything to fix the problem. But I'm hoping we can find a better way next time. To be clear I am not blaming anyone and you can't help everyone, but just something we can all consider

[JmOz01]

So the Magic C mage has 5 spells and a new spell after each run. The Magic A mage has 10 spells and a new spell after each run. With these assumptions:

1. MAG C will never catch up in terms of total spells. Of course there are diminishing returns to this point.
2. MAG C needs to spend karma on spells rounding out spell competency. MAG A provides a rounded enough spell list that one can safely beeline for initiation.
3. MAG C will be at a disadvantage, possibly a major disadvantage, all those runs in terms of versatility.

You will not convince me that 5 spells is enough. Especially if you're a pure magician and not a MysAd. On top of free skill points for skills you needed anyway.

Mages WANT to have a bunch of skills like everyone but only truly NEED so many. Assensing can be minimal as it's threshold, not opposed. Low Spellcasting and you're useless. Low Counterspelling and your team gets fragged. Low Summoning and you have piddly spirits. Binding is optional but with a CHA Mage you are giving up the best force multiplier in the game. Perception and the ability to shoot ok are good for everybody, and are opposed. This list includes needs and wants.

Arcana is more than safe to buy a point with karma. More than 1 isn't really necessary til you initiate a few times and you have plenty of runs to build up XP for that.

As to the group points...I'd put them in Stealth or perhaps Athletics. Stealth would be my first pick though.

I will point out that there is a maximum number of spells you can get (12 at magic 6).  I still feel that giving up 3 edge is a fair exchange for a lot more skill points.  Like they say everything comes at a cost.  The real goal should be what will make you have the most fun at the table

[Overbyte]

At least we stopped short of a Nazi reference... oh damn I just referenced the Nazi reference.. does that count? 

[Whiskeyjack]

I still feel that giving up 3 edge is a fair exchange for a lot more skill points.  Like they say everything comes at a cost.

It depends on how you use the skill points. Not all skills are created equal. Some are quite niche to borderline useless. This isn't the players' fault or even the GM's, but it is a consideration. Automatics and Perception are likely to be more relevant in more games, or even more game sessions, than Diving. Sure you might have one mission or one game session where Diving is relevant, but then you're allocating limited resources to a lower chance, and possibly no payoff ever.

I also don't believe in buying "fluff skills" or buy into notions that "everyone should have Computer 1" etc. I feel like too many people assert you need to either devote skill points or even make rolls for very common things that people do. Not everything needs a roll; I say the only time you should be rolling is where there is either a relevant time crunch or a meaningful chance of failure. You shouldn't need to roll to Google search a restaurant, nor should you need Computer to be able to do so without a roll at a baseline.

Anyway.

I assert that 3 EDG is usually going to be a better deal than niche skills, and probably more likely to save your life or pull off a long-shot action, but it also depends on what skills you're going to have at that point.

The real goal should be what will make you have the most fun at the table

True, that said, I don't play most RPGs in order to be weak and lacking much agency (Dark Heresy aside). I don't enjoy that play style (though if you do, more power to you). I'm approaching what I think is a good build from the perspective of my play style (as I think most people are approaching it from their play style) and, in the end, we all have different preferences. For me, it's not fun to be bad at my specialization, even if I'm not good at everything (which I don't expect to be). But if someone wants a pure mage build, I'm going to assume they want to be a super-effective mage, with no consideration to secondary skill-sets; that said, everyone, even pure mages, benefit from something like Perception 6.

[Overbyte]

I still feel that giving up 3 edge is a fair exchange for a lot more skill points.  Like they say everything comes at a cost.

It depends on how you use the skill points.

I agree with both of those statements.
Apparently I'm in an agreeable mood this morning. 

I think it all comes down to character concept and table. My characters (both PC and NPC) are always built off some (usually odd) concept so the entire build is done with that in mind. I even write most of my PC origins down in a short story (like those in the source books). This helps me both write up the character and play them. I would probably take extra "fluff" skills over 3 edge in almost every circumstance because it would round out my character. However, I play in games with only a few players, so being versatile is more valuable than other tables where being a specialist is better. At those big tables everyone needs to have something they are better than everyone else at, while at a small table everyone could have the same skills and still shine.

[Glyph]

Asking for a "pure mage" build is kind of vague, but I interpret it as a mage without any hyphens (mage-face, mage-covert ops, etc.).  So a pure mage would have nothing but magical skills, except for the basics any shadowrunner should have (perception, etiquette, sneaking, etc. at a lower rating than the core magical skills).

Mages resemble technomancers in one way - they have a lot of skills associated with them, but people who have used them in play tend to pare these skills down based on how useful they are.  The low-skill builds tend to be the pared-down ones.  They give you decent Attributes, high Edge, a magical focus, 10 spells, and high dice pools in the most important magical skills.  Overbyte's build has even better Attributes, but low Edge (assuming all of the special Attribute points are spent to raise Magic to 6), 5 spells, and no foci.  So at a cost of Edge and foci (and spells - although 25 Karma could close that gap), the build has better skills and Attributes.  Even with 36/5 skills, though, you will still need to narrow down your magical skill choices, since there are 12 magical skills (3 skill groups and 3 stand-alone skills).

[Overbyte]

I put the 5 skill group into either Sorcery or Conjuring, depending on what (if any) specializations I want to take.
E.g. - if I want the char to specialize in combat spell-casting I would put the 5 group in Conjuring and have a 6(8 ) Spellcasting (Combat).
Because of the low numbers of players its hard to imagine a build that is really "playable" that has E skill pick at our table, but I can certainly imagine it working at a large table where you have a very narrow responsibility. And I personally would never play a character with that little "depth" or actually I suppose it is "breadth". 

[JmOz01]

Ironically I have a character I have been working on for my wife Who is close to a straight mage.  Obviously some shifting of thins around but it should give you a starting point at least.  Probably a little more face than you would want, but a few minor changes...



Charm
METATYPE: HUMAN
B 3, A 4, R 2, S 1, W 5, L 3, I 6, C 4, ESS 6, EDG 2, M 6
Condition Monitor (P/S): 10 / 11
Armor: 12
Limits: Physical 3, Mental 6, Social 7
Physical Initiative: 8+1D6
Astral Initiative: 12+3D6
Active Skills: Alchemy (Command +2) 6, Archery (Crossbows +2) 6, Assensing 6, Con (Seduction +2) 6, Influence Group 4, Perception 6, Sneaking (Urban +2) 6, Sorcery Group 6, Summoning 6
Knowledge Skills: "Fixers" (Seatle +2) 4, Magical Communities (Seatle +2) 4, Magical Theory 3, Street Gangs (Seatle +2) 4, Vice (Seatle +2) 4
Languages: English N, Or'Zet (Street +2) 4
Qualities: Chaos Magician, Day Job (2,500¥/month, 20 hrs/week), Distinctive Style: Provocative Dress, Focused Concentration (4), Incompetent: Firearms Group, Mentor Spirit: Chaos, School of Hard Knocks, SINner (National SIN): UCAS
Spells: Flamethrower, Increase Charisma, Magic Fingers, Physical Mask, Stunball, Trid Phantasm
Alchemical Preparations: Heal, Increase Reflexes, Mind Probe, Opium Den
Gear:
. . Armor Jacket
. . Backpack
. . Certified Credstick, Standard
. . Flashlight
. . Glasses (1) w/ Image Link
. . Meta Link Commlink w/ Mapsoft: Campaign City, Sim Module, Modified for Hot Sim
. . Metal Restraints x2
Weapons:
. . Heavy Crossbow [Crossbow, Acc 5, DV 10P, AP -3, 4 (m)] w/ (8x) Barbed Bolt, (4x) Bolt, (4x) Explosive Bolt, (4x) Hammerhead Bolt
. . Ranger Sliver Pistol Crossbow [Crossbow, Acc 6, DV 12S(e), AP -5, 1] w/ (5x) Stick-n-Shock Bolt w/Static Shaft
. . Survival Knife [Blade, Acc 5, DV 3P, AP -1]
Contacts:
Fixer (Connection 4, Loyalty 2)
Knight Errant Dispatcher (Connection 3, Loyalty 3)
Starting ¥: 3D6 × 60¥

Hero Lab and the Hero Lab logo are Registered Trademarks of LWD Technology, Inc. Free download at http://www.wolflair.com
Shadowrun © 2005-2015 The Topps Company, Inc. All rights reserved. Shadowrun is a registered trademark of The Topps Company, Inc.

[Glyph]

I put the 5 skill group into either Sorcery or Conjuring, depending on what (if any) specializations I want to take.
E.g. - if I want the char to specialize in combat spell-casting I would put the 5 group in Conjuring and have a 6( Spellcasting (Combat).
Because of the low numbers of players its hard to imagine a build that is really "playable" that has E skill pick at our table, but I can certainly imagine it working at a large table where you have a very narrow responsibility. And I personally would never play a character with that little "depth" or actually I suppose it is "breadth". 

Skill: E builds can summon spirits for a variety of purposes, have 10 spells that can do a wide variety of functions, can scan auras and scout astrally, and can block incoming hostile spells.  And they can have some basic functionality outside of their specialty.  Of course, my own Skill: E builds have the 10 bonus skill points from Magic: A, and I also usually spend a decent amount of Karma on additional skills.