Starter Skills
On a fresh character you'l want to start with the basic skill gems available such as 
Firebolt / 
Spark / 
Freezing Shards / 
Flame Wall until you can get your hands on 
Frostbolt which pairs very nicely with 
Cold Snap and . 
Ice Nova is also a very nice addition to the build so be sure to get hold of this when you can as well.
Skill Gems
Frostbolt is useful when you pair it with Scattershot and Unleash giving a decent amount of early game damage. Later on 
Unleash will be removed in favour of other gems. Wildshards along with Cold Penetration should be equipped when available adding omni-directional damage and Cold Resistance Penetration to the build. Arcane Tempo is useful for raising your cast speed until this can be solved elsewhere. After you have enough Cast Speed you can swap this for 
Glaciation to raise the Freeze capability of the build. Deceleration can be used to reduce the projectiles speed, creating a moving wall of projectiles that you can stay behind. This can be furter slowed in the passive tree through the notable 
Turn the Clock Back.
Frost Bomb was very strong early on for killing groups of enemies and bosses. Spell Cascade and Second Wind can be added to further the damage output which I found to be super helpful.See AlsoMore don't-miss stories from Macworld – Page 387Call of Duty: Modern Warfare III PC Trailer, Specs, Preloading Info, and MoreNvidia reveals detailed ray tracing differences, promotes DLSS 3 for Indiana Jones and the Great Circle
Frost Wall is extremely useful because it can be used to block swarms of enemies, or you can plant it under the enemies feets for extra damage. It's especially useful against large hit box enemies where it instantly explodes under their feet for pretty significant damage and Freeze Build Up. Combined with Fortress to give the ability to block enemies within it and the utility of Font of Mana for Mana Sustainance, this is a must have in the build. You can take Icicle to reduce the crystals life if you want to use it as a more offensive option. Later on You can replace Fortress for Ingenuity for faster cooldowns.
Hypothermia Is the bread and butter curse in the early game to help deal with Cold Resistance mobs. The one thing to note here is that this can reduce enemies resistances below 0% allowing you to do extra damage. Cold penetration does NOT reduce below 0% in POE2 like it does in POE1 so this curse is useful even if you can penetrate all of an enemies resistances. Most of the support gems here are focused around increasing the area effect of the curse. The main ones are Magnified Effect and Persistence to achieve both a larger area and a longer duration. Later down the line you can get hold of Cursed Ground which turns the curse into a persistant ground effect with no activation delay and Ritualistic Curse for further area increase at no detriment if you have Cursed Ground already slotted. Heightened Curse can be useful in increasing the strength of the curse but I would avoid this if you're having Mana Sustain issues.
Cast on Freeze adds a layer of automation to the build focused mainly on group clearance. Everytime you freeze an enemy you will gain energy towards activating the skills slotted inside it, and later on you can achieve activating them very frequently with the right setup. I would recommend 
Cold Snap here to start with as you won't have access to 
Ball Lightning at this stage. 
Unleash and Inspiration are taken early to double up the offensive activation whilst mitigating the mana pressure this can put on the build. Later down the line there are support gems that can be used to improve the activation rate such as Impetus and Energy Retention. Once 
Ball Lightning becomes available you will want to replace 
Cold Snap as it's jsut extremely useful later on and 
Cold Snap seems to flatline damage wise in the end game. 
Ball Lightning allows us to be able to teleport to the projectiles with 
Lightning Warp as well as giving us the ability to apply Shocked Ground through this interaction much more easily. It also allows us to integrate Ailments into the build such as Electrocute which would be very useful in the higher endgame content.
Lightning Warp is a very useful utility skill that may seem out of place but what it allows is for us to integrate Culling into our build, including against bosses. It also gives us the ability to add Shock into our build once an enemy is culled which increases our damage against enemies whilst affected. In conjunction with Considered Casting for Huge Increased Damage, Soul Drain for extra Mana Sustain and Overcharge to increase the Potency of the Shock, this ability has incredibly utility value here. With the addition of 
Ball Lightning we are now able to activate 
Lightning Warp on demands towards the projeciles, using it as an offensive and a utility option for moving around the battlefield and apply Shocked Ground much more frequently. This ontop of the Culling tech means you can teleport around the map during combat to get in and out of combat situations as you see fit.
Eye of Winter becomes available at level 52 and is very strong. Cold Exposure is useful for near permanent cold exposure application on Critical Hits, Elemental Focus is taken more raw damage whilst costing some the ability to apply ailments (we can solve this elsewhere) and Fork is taken to allow the projectiles to split off to other enemies at the cost of 50% Damage after Forking. One thing to note here is we have both Chilled Ground and Shocked Ground in the build, so it can inherit these effects and apply them to all surrounding enemies with ease if you take off Elemental Focus and replace that with something else.
Arctic Armour is a useful tool you can add earlier in your playthrough once you get the 100 spirit cap from the side objective. This is useful to help prevent melee attackers from spam attacking you by potentially freezing them when they hit you. This is further increased by the use of Glaciation. The use of Clarity gives us 30% more Mana Regeneration and Bludgeon can be useful to prevent Perma-stuns by Knocking Back enemies when it activates. This is later replaced with 
Blasphemy once you can get to a minimum of 120+ maximum spirit, but preferably 130+ maximum spirit.
Blasphemy combined with 
Enfeeble is a very powerful combination that allows us to entirely bypass Curse activation restrictions in favour of a Reduced Strength Curse that acts as an aura around us reducing enemies damage against us. This can later be used to have permanent activation tools such as Clarity for Mana Regeneration. This can be used without Clarity so that you only require 120+ Maximum Spirit to use this in conjunction with 
Cast on Freeze but the extra Mana Regeneration is highly recommended. For 
Blasphemy to be able to be taken in the build alongside 
Hypothermia the Key Passive 
Whispers of Doom is required as this allows us to have 2 Active Curses at once at the cost of Double Activation Delays. The great thing here is that 
Hypothermia later on will use the support gem Cursed Ground to turn it into a persistant ground effect and 
Blasphemy will be turned into a constant Aura so both of them bypass Activation Delays entirely, meaning is just a benefit to us with no downside.
Comet is used now as a Manual Casting Ability rather than an On-Cast Ability. This in Conjunction with Spell Echo, Unleash and Arcane Tempo make it a deadly engagement tool once 
Frost Wall has been placed down to control enemies advancing upon you as well as being a good burst damage tool when larger enemies are Frozen. Later on Inevitable Critical & Supercritical can be equipped to supercharge the critical power of the comet skill if you choose to stack some Critical Chance and Critical Damage on your character.
Skill Info
The bread and butter of this build is to Freeze enemies using 
Frostbolt / 
Frost Wall / 
Arctic Armour / 
Eye of Winter as quick as possible to activate 
Cast on Freeze that will then activate either 
Cold Snap or 
Comet to clear waves of enemies.
Mobbing should be pretty straight forward and is definitely where this build excels more than bossing in the early part of the game. 
Frostbolt has such a high ability to Freeze with it's Chilled Ground effect that 
Cast on Freeze will activate fairly often. Both 
Cold Snap and 
Ball Lightning work here but since patch 0.1.0d it's now slower to activate skills so Energy Generation will be important to allowing consistent gameplay. 
Ball Lightning allows us to integrate Electrocute into the build as well as giving us Mobility options since you can teleport onto the projectiles using 
Lightning Warp, leaving behind extremely potent Shocked Grounds boosting our damage across the build in favour of doing big hits from 
Comet which now doesn't activate as consistently.
Frost Bomb is also useful for clearance and bossing if you can keep the enemies in place long enough to benefit from it. This is particularly strong in the early game before you can unlock many of the other skills or support gems so make good use of it!
Comet is still used in the build for its extremely devastating clearance ability as well as decent single target damage. Paired with Spell Echo it grants it devastatiing focused target area damage and by adding Arcane Tempo as well as stacking Cast Speed across the build will help with being able to cast this more frequently.
Eye of Winter can also be used to apply freeze if fired over the Chilled Ground effect that is left behind by 
Frostbolt as well as being able to apply shock if fired over the Shocked Ground effect that 
Lightning Warp creates, so bare this in mind for easy ailment application. Note: This will only work if Elemental Focus is not used on it, so be weary of this.
Hypothermia is best used when the enemies are not moving much or locked in place to maximise its potential. When you Freeze an enemy is a good example of when to use this.
Mana Stacking
This starter build doesn't play entirely into the mana stacking tech as mentioned above as we don't take 
Mind Over Matter & 
Eldritch Battery by default.
It does however have Arcane Surge on by default from the ascendancies as well as 
Arcane Intensity in the passive tree. What these allow are the ability to scale your cast speed, mana regeneration and damage through stacking mana so it's important to try prioritise this where you can.
The Endgame Variants choose to take both of the above key passives are taken which also scales the defensive capabilities of the build as well. This requires a minimum of 800 - 1000 Maximum Mana for the Early Endgame Variant and recommended 2500+ Maximum Mana for the Mid/Late Endgame Variants.