Level 87 Hybrid Crit Frostbolt Occultist^3.25

Notes

NOTE:
All of the rare gear in this build is just an example. You do NOT need to get rare gear exactly like mine, or even close to it. 
These are example stats of what you want. Most armour gear will want some combination of life, resistances, and other defences (hopefully mostly ES and armour, but socket colors and links are more important early). This is for the purpose of increasing your max hits as seen on the left in PoB

From the lab after Act 3 onward, you can search for Ice Nova of Frostbolts and try to snag one early if you get a good gem from the lab, or if you get some early currency. It's nice to have and boosts your DPS a ton early, but not vital by any means. 
IF you do get one early, throw frostbolt + volley in somewhere. If you have extra links, throw faster casting and/or returning proj on. You can buy returning proj in Act 4 after killing Malachai

CAMPAIGN:
ACT 1:

REGEX: 

b-b-g|b-[bg]-b|g-b-b|nne|singe

Use Rolling Magma + Ele Prolif + Arcane Surge until after Fairgraves when you get Ice Nova

Sockets:
2b1g for ice nova + arcane surge + added cold
1b1g for FB + added cold
2 random blues for frost bomb and clarity 

Grab Increased Critical Strikes and start leveling it

Look for a sapphire ring before mervail. Helps a lot in the fight. You can vendor an iron ring and a blue skill gem for a sapphire ring
Get a Jade amulet for the dex. You'll need it for leveling added cold damage gems. 

ACT 2:
Grab Herald of Ice
Grab Frostbite
Buy cold snap before the vaal ruins. Use the corrupt altar on cold snap. See if you get lucky. If no vaal cold snap, cold snap is fine. 
     Note: Cold Snap is used to generate frenzy charges. It also does good damage if you wanna use it for clearing. I don't worry about frenzy charges much until I get the charge mastery sometime in Act 4.

Grab Increased Critical Damage support and Power Charge on Crit support and start leveling them in an offhand weapon

ACT 3:
Grab Zealotry and start leveling it. Don't turn it on until you have some mana reservation either from the mana mastery or the mana reservation nodes 
Look for a 4b or 3b1g piece of gear for Ice nova

Optimal 4 socket Ice Nova at this point is Ice Nova > Arcane Surge > Increased Critical Strikes > Increased Critical Damage
Can also do Ice Nova > Added Cold > Increased Critical Damage > Increased Critical Strikes

Can also do a 3b1g 4 link with Frostblink. It's surprisingly effective through the campaign and early maps on trash mobs with Herald of Ice.
Frostblink > Increased Critical Strikes > Increased Critical Damage > Added Cold Damage

4 link Cold Snap is also really good at this point. Cold Snap > Hypothermia > Added Cold > Bonechill (act 4, can use arcane surge until then if this is your main skill)
    
ACT 4: 
Grab Bonechill Support and link it to Cold Snap. You'll want to hit tankier mobs with Cold Snap and curses first, then use Ice Nova on them. Frost Blink to dodge and for more damage whenever the CD is up. 
grab spell echo and lightning golem
Get spell echo before fighting malachi. It'll make the boss fight many times easier

Sometime during this act is when you'll get the charge mastery for increased duration. Big QoL for keeping your power and frenzy charges. 

Optimal links in act 4:
4b ice nova
4b arcanist brand + curse setup
2b bonechill + cold snap
frost blink
clarity
herald of ice
1b3g or 2b2g IF you're using frostbolt. Otherwise no need to worry
ice golem can be useful if you have a socket

PSA: Don't link support gems to herald of ice 

ACT 5:
Try to get your resistances ready for the -30% you get from Kitava. Nothing else new this act. 

ACT 6:
Grab these gems after Lilly's quest and start leveling them in an offhand.
Inspiration
Flame Dash

You can use Shield Charge + Faster attacks at this point as well to get through the rest of the campaign faster. You'll want to drop the dual wielding nodes as well. I often just continue using frost blink and running. 





Start working on gem links and aura set ups over the next few acts:

Ice Nova of Frostbolts > Spell Echo > Inspiration > Increased Critical Strikes > Increased Critical Damage 
     Drop Increased Critical Strikes when your crit chance is over 60% without it.
     Once you start getting past ~60% crit chance, you can drop the chance to freeze nodes on the tree to free up some points, as cold damage crits have 100% chance to freeze

Frost Bolt > Volley > Returning Proj (or slower proj)

Steel Skin or Molten Shell > Automation

Shield Charge > Faster Attacks

Arcanist Brand > Frostbite >  Frost Bomb > Elemental Weakness

Vaal Cold Snap > Bonechill 

These don't need to be linked:
Herald of Ice 
Zealotry 
Flame Dash (whenever you decide you don't wanna use Frost Blink any more)

If you have extra sockets, can throw these in:
Frost Shield
Sigil of Power

/CAMPAIGN

Good unique weapons to look for: 
Reverberation rod - cheap and effective. Can be used in the acts and up to early maps. Very mana hungry, so might need to alter your passive tree to get more mana and mana reduction early below the witch starting point. 
Tulborn - These are a breach unique drop, so the first few will be a bit pricey and then they'll quickly go down in price
Tulfall - upgraded tulborn. This is my weapon of choice, but you'll want ralakesh boots before using this
Void Battery - Always a good option for charge stacking. Expensive early.
Divinarius - can farm yourself with divination cards. A bit pricey early but usually goes down after a few days. Excellent choice for sustain.

Mark of Submission with Frostbite is a huge, cheap QoL change once you do 4th lab and get Profane Bloom. Can upgrade to another curse on hit ring later, or gloves with curse on hit. Corrupted surgebinders are a good option. Or asenath's gentle touch for more explosions.

WHEN YOU HAVE CURSE ON HIT:
Change the arcanist brand to either Frostbite or Ele weakness (whichever isn't on hit. Or if it's neither, then just drop ele weakness) > Bonechill > Cold Snap. One less button to push :)


EARLY MAPS:
Decent wand with either + to all gems or cold skill gems, cast speed, crit chance, spell damage, etc. for leaguestart. It does NOT need all of these affixes.


Consider grabbing Eldritch Battery so you can ditch the mana flask. Might hurt your survivability too much, depending on your gear. At some point, you'll get your mana costs reduced enough that you can ditch EB
Grab some spell leeched as ES

Cap resistances and get needed attributes
Fill out life/es nodes on passive tree
Swap to at least a 5 link ice nova


LATE MAPS:
Swap to a 6 link ice nova
Continue upgrading gear for defenses and damage
Save up for chase items, in whatever order you want to go, such as Ralakesh boots, Aegis, Malachai's loop,  +1 power charge ring, mageblood, headhunter, etc. 



UPGRADE PRIORITIES THROUGHOUT MAPS IN ORDER:
Cap Resistances (if not capped already)
Good weapon (tulborn, divinarius, tulfall, or +1 wand with spell damage, cast speed, etc). Can even use a staff if desired, and drop shield charge for leap slam. Pledge of hands is an excellent choice. 
Flasks
Swap to a 6l Ice Nova of Frostbolts
Attributes
Quality on gems



Breakpoints: 
Act 3 - try to get ice nova of frostbolts

Act 4 - spell echo. You'll want to be running a fairly high level clarity at this point and have mana regen nodes allocated. This is only if you got an early ice nova of frostbolts

3rd lab - You'll want to have the charge mastery cluster and both + to max power charge nodes taken by this point 

around this point you should have enough crit chance to drop chance to freeze nodes

6 link ice nova 

Once you get a decent 6 link, decent flask setup, and a good wand, you can do t16 maps pretty easily.



Cheap uniques to keep an eye out for that are helpful for early maps or campaign:
Tulborn (breach boss only drop, so not likely to see day 1 of leaguestart) 
Light of Lunaris
Zeel's Amplifier
Reverberation Rod

Uniques to keep an eye out for once you get to maps: 
Void Battery
Tulfall
Malachai's Loop
Ralakesh boots
Tulborn
Divinarius
Surgebinders
Willclash