A
troll shadowrunner with a bardic focus.....? That's....wierd, at least.

Sorcery will be the
only way he's going to influence anyone positively. :\ On the up side, he may be the leader of a troll thrash metal band?
You'll need to give more info, anyway. Shadowrun 3rd Edition, or 4th Edition, or earlier? If SR3, is the Shadowrunner's Companion (if I recall the name correctly) being used? These will be kind of important.
I only have SR3, and not the Companion, so my own response will be kind of limited....
Stat-wise, your priorities will probably look like this:
A-magic, B-attributes, C-race, D-skills, E-resources, or
A-attributes, B-magic, C-race, D-skills, E-resources
It depends of course, but......your concept is tough. If you avoid summoning-related stuff, you can go for an Aspected Magician, using priority B for Magic instead of priority A (which is for Full Magicians). You might swap the priority of attributes with skills, or skills with resources, but I don't think it would serve a bardic concept well.
As a troll mage you'll need high base scores in your mental attributes (at least Int and Will) since the choice of race will put a penalty to Int and Cha. Still, it
is doable, putting attributes at priority D if you really need the skill points or nuyen for gear (you really won't fare well at trying to use
skills for persuasion and such, as a troll; in addition to the Charisma penalty, normal humans and some others will just react poorly to a troll).
The choice of Shaman or Mage doesn't matter much, but they do kind of determine how you'll interact with other people. The Cat, Coyote, Mouse, Raccoon, Rat, or Raven totem would be reasonably appropriate to a sort-of-bardic Shaman.
If you go for an Aspected Magician, then Sorcerer is what you should choose as your aspect (spirits or elementals won't help you so much or so often in the stuff a bard-like character would be doing).
You'll want to maximize your Willpower attribute. Intelligence and Charisma are hurt by being a troll, but they're also important to your Spell Pool and Astral Combat Pool dice. I don't know if you plan on doing any Astral scouting/fighting, so you may keep Charisma minimal if you avoid Astral combat (it doesn't apply to Spell Pool). Still, thematically Charisma should matter to a bard sort of character.
Besides those, try to make your Quickness decent or good, since it will matter for skills like Stealth. Body will also matter for keeping you alive. Don't worry about Strength. Quickness only needs to be decent, though Body should preferably be a bit higher.
To pull off a bardic shtick, he'll need primarily Illusion spells and Control Manipulation spells. Probably also a few Detection and Health spells.
Mind Link, Mind Probe, and Combat Sense may be fitting Detection spells, though Mind Probe is considered.....well, very bad in the Third World (not in the effectiveness sense, but....). Any or all of those three could be useful.
Decrease Attribute or Decrease Cybered Attribute may be fitting Health spells (of the offensive sort....making an opponent weaker in combat). Treat, Increase Attribute, Increased Cybered Attribute, Increase Reaction, Increase Reflexes, Resist Pain, or Stabilize may also be suitable. So pick two or three that may suit your character (i.e. do you want to focus on buffing, or helping allies survive/recover, or weakening foes, etc.).
Detox and Healthy Glow are thematically appropriate, though I'm unsure how often they'll be helpful. As for Illusion spells, you could go with two or three amongst Mass Confusion, Improved Invisibility, Physical Mask, Trid Phantasm, or Silence. Among the Control Manipulations, the spells Control Thoughts and Influence are probably most useful for you.
Besides that stuff, it's possible you may want to learn Stunbolt or Stunball, which are kinda like Sleep in D&D since they serve to just knock people unconscious; surprise someone or sneak up on them, then render them unconscious with Stunbolt or Stunball.