Level 100 Tornado Shot Pathfinder^3.21

Notes

CORRECTIONS:
The Attack Mastery skill point, "Gain Adrenaline for 1 second when you change Stance," has been preemptively removed from the game prior to launch due to community backlash.
As described in the video, a good alternative is to move that skill point over to the Aura Mastery, "8% increased Damage for each of your Aura or Herald skills affecting you," and switch Blood and Sand out for Defiance Banner.

BANDITS & PANTHEON:
The priority is passive skills and improving defenses.
Bandits: Kill all
Major God: Soul of Arakaali
Minor God: Soul of Ralakesh

LEVELING:
Use the Skills and Items section under Poisonous Concoction to gain an idea of how best to outfit your character as you progress through the campaign and into maps. Just recognize everything is tailored more towards an early endgame setup.
Leveling in the campaign is pretty straightforward. After killing Hillock, choose between with Galvanic Arrow or Caustic Arrow as your primary damage ability. Use this until you unlock Poisonous Concoction at the end of Act 1.
The loss of 10 life on hit and 5 mana on hit from the Claw mastery means you'll want to run Vitality and or Clarity gems early on in the campaign. Blood Rage can be dropped at any point if it's causing life recovery issues.
As of patch 3.21, Poisonous Concoction suffers a loss of 30% increased AoE from the Ascendancy and now endures rising life charge cost per projectile per attack. Both of these nerfs are circumvented greatly by swapping the traditional Greater Multiple Projectiles support out for another damage support gem.
Use Poisonous Concoction all the way into red maps. If you manage to acquire a 6-link, Deadly Ailments support will likely be the best choice for the final gem slot.
If at any point you find yourself shy on attribute requirements, you can always sacrifice a point or two for the +30 strength/intelligence nodes nearby.

SWAPPING:
This guide assumes you will not be swapping to Tornado Shot until you're at least level 88 and have already have Darkscorn, Ming's Heart, and Zerphi's Heart on standby.
Killing bosses and doing Maven invitations is likely to be less of a challenge with Poisonous Concoction than Poison Tornado Shot, so bear that in mind when timing your swap.
Once you begin using Darkscorn, you'll want to make sure your chaos resistance is capped or very close to it. You can forgo Magic Finding gear in favor of more standardized rare gear to achieve a much smoother transition into the build.

UPGRADING:
Here are some strong but expensive upgrades to consider that go beyond the budget of this "league start" build guide (in no particular order of importance).
1) Reaching maximum quality on all gems that provide some benefit from it
2) Acquiring perfect or near-perfect rolls on all flasks.
3) Leveling and corrupting cheaper gems for a chance at a level 21 gem (priority Tornado Shot, Plague Bearer, Grace)
4) Swapping damage support gems for their Awakened gem counterparts
5) Divergent Tornado Shot for increased attack speed
6) Anomalous Blood Rage for Frenzy charges against bosses
7) Divergent Plague Bearer for added global chaos dot multi
8) Anomalous Purity of Elements for increased aura effect
9) Divergent Vaal Haste for increased projectile speed
10) "Tornado Shot Fires an Additional Secondary Projectile" helmet enchant for 25% more DPS (preferrably as a base to be crafted)
13) Squeezing in an Enlighten support and adding anadditional aura
14) Pairing the corrupted implicit on amulet "You can apply an additional curse" (or Whispers of Doom anoint) with a good corrupted implicit on gloves like Despair or Enfeeble on hit
15) Corrupting Ming's Heart for a much more potent implicit (such as "Bleeding cannot be inflicted on you" or "+% increased Quantity of Items found")
16) Socketing a massive wheel Thread of Hope near the Ranger starting area for more powerful passive skill point allocation opportunities
17) Adding a high-value Lethal Pride or Brutal Restraint to the Ranger side for a more traditional high-end skill tree setup
18) Getting Expedition's End, thereby unlocking Freeze to an already large list of ailments
19) Crafting a better helmet with more rarity and mana reservation efficiency
20) Crafting a better quiver with more life and bigger damage rolls
21) Crafting a high-end physical DPS Spine Bow to replace Darkscorn for more overall DPS, resulting in a move away from the poison cap towards more hit-based damage (see unused items)
22) Swapping Bisco's Leash for Headhunter or Mageblood and using a Sinvicta's Mettle weapon swap to retain Rampage while also gaining massive amounts of AoE

PRICES:
Prices are subject to fluctuate wildly on account of builds gaining unforseen levels of popularity. In the case of this build, Darkscorn and Zerphi's Heart are especially susceptible.
For reference, these are the following prices from day 7 of the previous league on softcore trade, courtesy of poe.ninja. Prices will be much higher for perfect or near perfect rolls.
Darkscorn: 8c (likely to be much higher)
Daresso's Defiance: 2c
Asenath's Gentle Touch: 16c
Goldwyrm: 2c
Zerphi's Heart: 18c
Ming's Heart: 5c
Ventor's Gamble: variable
Bisco's Leach: 2c
Dying Sun: 40c
Divination Distillate: 2c