Goblin Electromancer — ruling 1

To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.

Goblin Electromancer — ruling 2

Goblin Electromancer's effect reduces only generic mana in the spell's total cost.

Goblin Electromancer — ruling 3

Two Goblin Electromancers will make instant and sorcery spells you cast cost {2} less to cast, and so on.

Goblin Electromancer : règles, fonctionnement et interactions (MTG)

Goblin Electromancer is one of those cards players keep asking about. Here is, in plain words, what its official text says, the rulings published by Wizards of the Coast, and the combos players actually run.

Official card text

Instant and sorcery spells you cast cost less to cast.

How it works : Goblin Electromancer

Original English text — Wizards of the Coast / Scryfall

#1October 5, 2018· Wizards of the Coast
To determine the total cost of a spell, start with the mana cost or alternative cost you're paying, add any cost increases, then apply any cost reductions. The mana value of the spell remains unchanged, no matter what the total cost to cast it was.
No other card is named in this ruling.
#2October 5, 2018· Wizards of the Coast
Goblin Electromancer's effect reduces only generic mana in the spell's total cost.
No other card is named in this ruling.
#3March 14, 2017· Wizards of the Coast
Two Goblin Electromancers will make instant and sorcery spells you cast cost less to cast, and so on.
No other card is named in this ruling.