OK, let me try to answer your questions.
More summoning is more good, but not as much as more spellcasting is more good because summoning is binary - either the spirit appears, or it doesn't. Spirits roll F, you roll Magic+Summoning+Focus+Specialization, so it's easy enough to get spirits to appear. The limiting factor is drain and more summoning doesn't help.
Being a pure conjurer is a Bad Idea in very big ways. I don't recommend it. Spellcasting is very important, so are spirits, trying to rely only on one or the other is not going to work too well.
Good spells: depends what you want to do. Everyone should have Increase Reflexes. If you care even slightly about fighting, you should have Stunbolt, Stunball, and either Powerbolt or a single-target P-damage elemental spell (not having this means you can't hurt nonliving targets). There are lots of horrible Illusion spells and a handful of really good ones: Physical Mask and Trid Phantasm are very good spells. Detection and Manipulation are full of about an even mix of useful spells and crap. If you check the first link in my sig and look at the magicians, you can get some ideas of what I consider to be good spell selections.
Agility: Dodge doesn't rely on Agility, nor does movement. You add your Dodge skill to your Reaction when you are in melee, and you can blow your next action to add Dodge to both melee and ranged defense and reset your penalty for being attacked multiple times. It's very tempting to overinvest in dodge and overuse this, but it generally just makes you lose slowly. In particular, Body 2 will do a lot more for your not dying than Dodge. That said, Dodge is not useless and if you free up the points, Dodge 4 is worthwhile. Don't bother with stuff like Dodge 1, though, that will just tempt you to waste actions. The only thing your character has that's Agility-based is Infiltration and that's why I suggest cutting from it.
Re: Concealment and Assensing: it actually does work...sorta. You can use Concealment to conceal yourself from astral detection (ie, Assensing)...but only if you are dual natured. This means that your Concealment does reduce Assensing tests, but only while you are astrally perceiving. See SR4A 293.
You can also use Infiltration to hide from Astral perception - but again, only while dual natured (see the FAQ).
Astral Combat is of very marginal use.
You would probably be best off just being a Shaman. You really should have a Charisma tradition and it's the only one that sounds appropriate, and Shamanism is so incredibly broadly and vaguely defined that it can be whatever you want. You might also talk your GM into allowing a custom tradition but that may not fly.
