[2.2.2b] Cast when Drinking Potion spell spammer - 20 spells per second with no active skills

Weapon: CwDT + GMP + Ball Lightning + Arctic Breath + Ice Spear

The GMP helps more than any additional spell here - spells that fire individual projectiles are pretty terrible since they fire in a random direction and are unlikely to hit anything when unsupported, but GMP mostly alleviates this. An alternative that's probably just as good would be to run some more AoE spells here (Firestorm, Glacial Cascade, Shock Nova, etc.), possibly supported with Increased AoE - the reason I'm not doing that is because AoE spells work even without supports, so they're better for filling in random sockets.

As far as these particular projectile spells, Ball Lightning is picked because it's OP and hits everything in one half of the screen when linked to GMP. Arctic Breath chills enemies. Ice Spear is an arbitrary choice - starting to run out of projectile choices here (Magma Orb is probably just as good).

Hat: CwDT + Righteous Fire + Arc + Elemental Weakness

RF is used to increase spell damage of any spells that hit instantly and any spells that happen to hit while it's active. As for being in the hat, I haven't tested this myself, but I vaguely remember reading somewhere that CwDT triggers gems in your primary weapon and hat before your gems in other equipment, so RF being in the hat might matter.

Arc auto-targets enemies and requires no supports, so when it rolls a crit, it's a guaranteed flask charge since it'll never miss. Since you only get one flask charge per spell regardless of number of enemies hit, the fact that it'll only hit 3 enemies doesn't matter as far as The Harvest is concerned (it does matter for Voll's Protector though).

Elemental Weakness is mostly for single-target - it won't curse a large portion of the screen due to low AoE from being low-leveled. Any curse works fine here though - you can throw in any curse you want depending on what you're looking for (Temporal Chains, Enfeeble, Poacher's Mark). Moving the curse to its own 4L with a Curse on Hit setup is probably fine too.

Gloves (Voidbringer): CwDT + Summon Raging Spirit + Shock Nova + Ethereal Knives

SRS is a minion that will distract enemies; skeles also work (running both might also be a good idea). Shock Nova is another non-projectile/non-targeted spell that is likely to hit. EK is a projectile spell, but has a wide cone and doesn't need to be supported to consistently hit enemies. (Note that Voidbringer gives +1 to elemental gems, so you'll have to double-check that any gems in it are low enough level to be casted by CwDT even if they're low enough level otherwise.)

Shoes: CwDT + Discharge + Life Leech + Increased Area of Effect
Discharge is the highest damage spell linked by a fair margin, so it's worth supporting with Increased AoE despite being usable without it. Life Leech is a flex socket here - you can replace it with other damage spells or different supports, or even some Vaal skill that benefits from increased AoE (Vaal Molten Shell).

In general, the higher the level of Discharge+CwDT, the more DPS you'll do due to reduced CwDT damage penalties, but the damage will also be more inconsistent and makes you prone to reflect.

Using a lv8 CwDT + lv11 Discharge causes it to be triggered every two Doedre's Elixirs, which is around 5k damage per use on average (11k per hit / 2 uses). Using a lv20 CwDT + lv20 Discharge would yield higher DPS at ~7k damage per elixir use on average (50k per hit / 7 uses), but again opens you up to dying to reflect + isn't as good for <75 maps since the lower level discharge kills everything anyway.

Chest: CwDT + Ice Nova + Increased Area of Effect + Curse on Hit + Assassin's Mark

Curse on Hit + leveled Assassin's Mark are necessary somewhere, since Ass Mark massively increases the consistency/damage of the build, but what to use it with is up to you. I've chosen to use it with Ice Nova + Increased AoE; Shock Nova + Increased Area of Effect works probably the same.

Reasons for not picking some other links in the chest:
Level 1 CwDT + low level Discharge + Increased AoE: A Discharge that is low enough level to be triggered off of a lv1 CwDT will do pitiful damage, and you lose the ability to run a higher level Discharge on some other link. You'll also never have any power charges for increased crit chance on your other spells.

Level 8 CwDT + medium level Discharge + Increased AoE: Having a higher leveled CwDT means you need to use more elixirs before this link is triggered, but Ass Mark is important enough that you really want it to cast on every elixir use, not just every other one.

Ice Nova + some other active skill (with no additional support): Not sure if there's any active skills that would make this better than Ice Nova + Increased AoE.

GMP + Ball Lightning: If you're hard-casting your Curse on Hit trigger spell, this is definitely just the best option since you can curse a huge area in front of you as well as hit enemies off-screen. However, having it on a trigger gem means that it's going to mostly go in a random direction, which means that a decent amount of time it's just going to be aimed behind you where it hits 0 enemies.

Ice Nova + other curse: You really need Increased AoE.