It Grows Over Time! (IGOT)
Mana engine build. This build has a 32 hour minimum setup time. Excellent build to use after Lighting Forge. As of Version 1.5.42.6 you need about 1 Dvg (1E69)-5 Dvg (5E69) gems to reach R16 on a standard run.

Includes Variants: Longer and Longest run upgrades. These requires much longer setup times.

Range: R14 - R18
Requires: Autocasting, spell upgrades.
Alignment: Good
Bloodline: Fairy (2 Matches)
Spells: Fairy Chanting, Combo Strike
IGOT a Pickaxe variant: Replace Combo Strike with Diamond Pickaxe (IGOT a pickaxe)
Tier 1 Upgrades

Goblin (1,1): Strong Currency
Angel (1,2): Angelic Determination
Druid (1,1): Druidic Vocabulary
Dwarf (1,3): Mining Prodigies
[Low excavations—Titan (1,3): Oversized Legends]
Tier 2 Upgrades

Fairy (2,1): Fairy Workers
Angel (2,2): Angelic Wisdom
Titan (2,3): Cyclopean Strength
Druid (2,3): Shapeshifting
Tier 3 Upgrades

Faceless (3,1): Magical Treasure
Goblin (3,1): Goblin Central Bank
Fairy (3,3): Swarm of Fairies
Drow (3,3): Blade Dance
[if using Diamond Pickaxe variant—Dwarf (3,1): Battlehammers (source)]

Harlequin Bonus: 512%
Instructions (Copied from IGOT for dummies by sonicman54, based on this postby artcrow)

Note: Buying more buildings/exchanges/upgrades should be done as you can afford them, there is no ‘idle’ requirement you need to worry about breaking.
Buy all upgrades and spells above, then start autocasting Tax Collections until you reach about 135 assistants. It takes approximately 5 hours to get 135 assistants. (Using Battlehammers, ~17 hours, and if only using Holy Crusaders, the good merc upgrade, it takes 93 000 spell casts.)
At 136 assistants, Fairy Chanting should be added into combo, before TC, in one of two ways.
With Efficient AC (Bronze): Set contingency at around 97% max mana [Optimal amount may need testing], this will allow for very little downtime on Fairy Chanting and little need for micromanagement, but may cause for slower growth in mana regen.
Bronze: 1) Fairy Chanting - Silver: 1)Tax Collection.
With Priority AC (Silver): Set contingency arrow at around 910 mana, or to where it will trigger around two seconds after FC times out. Regularly requires micromanagement every so often as your mana regen grows.
Set the spells to cast in this order: 1) Fairy Chanting: 2) Tax Collection.
At 200 assistants, add in Combo Strike and lower the contingency arrow to 900. (for about another 18 hours until 270+ assistants)
With Priority AC (Silver): 1) Fairy Chanting: 2) Combo Strike: 3)Tax Collection
Alternatively, set: Bronze: 1) Fairy Chanting: 2) Combo Strike - Silver: 1) Tax Collection, and leave the contingency arrow wherever fits best.
At 270+ assistants, depending which auto-casting tools you have, choose:
Priority AC (Silver): Set Contingency arrow to 0. Set the spells to cast in this order:
1) Fairy Chanting, 2) Spiritual Surge, 3) Call to Arms, 4) Combo Strike, 5) Holy Light, 6) Tax Collection
Planned AC (Gold): Set the Contingency arrow to about 97% max mana, about one second before reaching max mana.
Silver: 1) Fairy Chanting, 2) Spiritual Surge, 3) Combo Strike, 4) Call to Arms
Gold: 1) Holy Light, 2) Tax Collection.
Efficient AC (Bronze): Set the Contingency arrow to about 97%, about one second before reaching max mana.
Bronze; 1) Fairy Chanting
Silver: 1) Spiritual Surge, 2) Combo Strike, 3) Call to Arms.
Gold: 1) Holy Light, 2) Tax Collection.
This will ensure Fairy Chanting is active consistently, allowing for minimum downtime and provide the best mana generated over time ratio. -Tip by Ragbash (talk) 03:33, March 27, 2016 (UTC)
Variants:

Longer run: use Dwarf (3,1): Battlehammers in place of Fairy (3,3): Swarm of Fairies. Requires about 55-60 hours of setup time.
Longest run – never attempted: Swap skills as in Longer run variant. Also use Dwarf (3,2): Magic Resistance in place of Goblin (3,1): Goblin Central Bank. Requires unknown number of days setup. Maybe 5? Read this or original post.
Note:

Build title comes from the Bearded Assistants upgrade, “Increase the production of assistants based on how long their beard is (it grows over time!).”
IGOT Template:
FR4,FR9,AN2,AN5,GB1,GB7,TT6,DD1,DD6,FC7,DN3,DW9,SP:Fairy Chanting,SP:Combo Strike
IGOT a Longer Run Template:
FR4,AN2,AN5,GB1,GB7,TT6,DD1,DD6,FC7,DN3,DN7,DW9,SP:Fairy Chanting,SP:Combo Strike
Low Excavations:
FR4,FR9,AN2,AN5,GB1,GB7,TT3,TT6,DD1,DD6,FC7,DW9,SP:Fairy Chanting,SP:Combo Strike
IGOT A Pickaxe Template:
FR4,FR9,AN2,AN5,GB1,GB7,TT6,DD1,DD6,FC7,DN3,DN7,SP:Diamond Pickaxe,SP:Fairy Chanting