Suggestions:

*Make sure invisibility is "Improved Invisibility."

*Heal or Treat. There's more to combat than killing - there's also surviving. Some sort of healing spell is one of the most useful spells a mage can have.
--Get a Medkit!! (Or one of those nanomedkits from Man & Machine). The combination of First Aid + spells is an enormously powerful healing system. Successful First Aid drops the injured by one wound level (like, 9 boxes/Serious to 3 boxes/moderate), then you can follow up with a spell to heal even the most cybered samurai down to Light, if not fully heal them. With a couple of minutes outside of combat, you can turn a mangled group of runners back into a fighting force.

*Get Mind Probe. It's an enormously useful spell that can gather all sorts of information in minutes that would otherwise take days of searching, bribing, and interrogating.

*Damaging spells are nice for combat mages, but remember that mundane weapons don't impose drain and can do the work of many offensive spells. Also, a few basic spells (manabolt, stunball) can accomplish most of the lethal/nonlethal damage a combat mage needs to deliver. So, when you pick your offensive spells, look for effects that aren't easily duplicated by weapons or "basic" spells:
--Replace stunbolt with stunball. Stunbolt is easily handled by a street legal taser, but the only weapons that can deliver area effect stuns are concussion grenades. Grenades can be hard to smuggle into secure areas and are a lot noisier than a stunball.
--Replace manaball with manabolt. Manabolt makes a nice, lethal "concealed weapon" that the average corp guard won't spot even with a full cavity search. You can use stunball to take down a lot of people at once and kill them at your liesure with a pocket knife or even your barehands.
--As for elemental manipulations...well, they're flashy and cool, but you can get most of your work done with manabolt, stunball, and mundane weapons, thus saving spell points for utility spells.

*Levitate could be useful, but I'd save it for later purchase. Spend a few points on the Athletics skill and consider some climbing gear until you have those spare spell points.

*Bullet barrier is nice, but body armor doesn't require concentration to sustain, so I'd save bullet barrier for later. Caveat: if you have some spell points left over, a generic barrier is one of those concealable "items" that a security guard won't find. If you plan on going places that frown on armor, barrier spells could be worthwhile.

*Makeover and Fashion are useful, but might be saved for later. They can clean you up in an eyeblink and change your appearance and clothing to help elude escape...and you won't need to sustain them, unlike Physical Mask.

You didn't mention the Force you are learning it at, so is this SR4? (in SR4 you can cast any spell known at any Force your Magic allows)

If this is SR3 you don't lose much by having Invisibility/Improved Invisibility at Force 1. Casting that spell at Force 1 is a standard cheese, as long as you are able to generate a large number of hits. If the number of hits you generate is larger than a mundane opponent's Int stat they have no chance of succeeding. Opponents that have Spell Defense coverage do throw a wrinkle into that, and sometimes you'll run have a tough time coming up with enough hits to stump Int 6 baddies. But generally this is good enough to get past the standard guards/mooks. The awakened are usually are tough nuts for a starting PC to fool at any reasonable level of drain. Depending on GM ruling, virtually impossible if they are observing in the astral.

EDIT: Some GMs rule that Inivisibility works on the astral, and Improve Inivisibility does not. Plus Invisibility has a lower drain. So if you have the points to spare Invisibility at a high force plus Improve Inivisibility at Force 1 covers a lot of territory.

Actually this example no longer works, it's been ruled out and the spells no longer exist in SR3.

What 'errata'ed' version? I find no mention of any changes (official or even just recommended) on the SR website, either in the Errata or the FAQ.

So, are you saying that, in your opinion, a character could not even be using a Sustaining Focus if he wants to Summon (or use any other Exclusive magical ability)? If so, I have to disagree with that. That is one of the main benefits of a Sustaining Focus. The mage is no longer sustaining the spell when he uses the Focus, so he wouldn't need to drop it.

This, on the other hand, is totally correct.

Then does that mean that any quickened sustained spells must be dropped as well? I see it as "dropping any spells you are sustaining". But I can certainly see how you can come up with that interpretation, although that interpretation opens up a larger can of worms than I am willing to accept.