For the Critical Mass passive, what is meant by the "chance" is that it is determined by the proc coefficient of the spell you cast. Single target spells have 100% "chance" to reduce the cooldown by 1 second while AOE spells have differing sets of proc coefficents by spell AND rune. There's a few sites that break down proc coefficents of various spells which applies to crit chance as well as return on LOH. Here, and here. Luckily people with more patience than me seem to have most spells crit proc chance figured out.
Some useful proc chances for popular wizard spells:
Hydra: 0%, Hydras never proc
Magic Missile / Seeker: 100%
Shock Pulse / Piercing Orb: 25% per target hit
Blizzard / Snowbound: 2% per tick per target hit
Energy Twister / Wicked Wind: 10% per tick per target
Explosive Blast / Chain Reaction: 11% per target hit per explosive (of 3)
I've recently been trying the Windup Wizard/CM build which still seems pretty effective, and a bit silly (in fact it was the easiest way for me to beat inferno Ghom). From personal experience I've found that on my wizard, when I run over 40% crit chance while using a build like windup wizard, everything is off cooldown pretty much all the time.
From the standpoint of your weapon: Weapon Damage is king. Above all else, you want the highest possible amount of raw damage and DPS possible. Beyond that, you'll want to take a look at this formula to understand the value of other stats.
In short: at low levels, nothing is going to beat raw +Damage on any slot where you can get it (Rings, Neck, Offhand). As you increase in level, you'll eventually reach a point of inflection where the multiplicative scaling gained from adding +Dex is more valuable than the straight + Damage. This point of inflection will vary with other stats, and particularly with the base DPS of your weapon - your best bet is to simply keep an eye on the +Damage portion of the tooltip when comparing items.
As for stats like Crit and Attack Speed, the same basic rules apply. In general, .1 attack speed is worth 10 Dex, but this ignores the defensive benefits of Dexterity, and since attack speed bonuses are provided as percentage multipliers, you'll need to do some math. You'll need to run similar calculations with +Crit and +Crit Damage, but in general, unless you use skills or passives that rely on Crit, you can assume those stats are less valuable than the others.
Really, all of this comes back to one key point: Trust the Damage Stat on your Character Sheet. So long as you're doing the basics right (using a level appropriate, high DPS weapon), it isn't going to steer you far wrong. Beyond that, Dexterity is King, and everything else depends entirely on the magnitude of the stat that you get. An item with +Crit might be better than an item with +Attack Speed, based purely on how much of it is there.
Best Answer
Your new question is fairly dependent on a lot of factors, but you want to start you build by looking at a combination of Ray of Frost (either Snow Blast or Cold Blood). Snow Blast is technically our highest DPS, but it takes time for it to ramp up. If you are doing hit and run, then Cold Blood will serve you better and leave you more mana to work with.
Magic Missile with Charged Blast is going to be your best single target Primary unless you are trying to trigger a proc of some sort. If you are, then Electrocute is were you want to look for that. A good primary is important to keeping the damage up while you regen mana.
For raw damage increase, Force Weapon is an obvious buff worth taking. Sparkflint will increase both your attacks and provide shots of its own.
Hydra is probably the best spell for adding additional single target damage for little mana. The other Force and Conjuration spells are geared more towards AoE. Conflagration will cause the Hydra to give you an additional 10% boost to your damage.
Slow time can be used to boost damage in several ways in addition to providing some defense. Stretch time will provide a nice 10% increase to attack speed.
Arcane Dynamo, Conflagration, and Glass Cannon are going to be the passives you want to look at first.
So to sum it up, assuming single target with no worries about survival here is a good start:
Ray of Frost (Snow Blast or Cold Blood), Magic Missile (Charged Blast), Magic Weapon (Force Weapon), Familiar (Sparkflint), Slow Time (Stretch Time), Hydra, Arcane Dynamo, Conflagration, Glass Cannon