Never mind what Louis Althusser would have said, and forget about Kemalism.
Let's peel off the bells and whistles and look at the bones of the sentence:
- Education is the most efficient apparatus [from which to gain the nation.]
The bracketed part is a Relative Infinitive clause modifying apparatus (the Antecedent of the relative clause), with a relative pronoun which that refers to apparatus and is the object of the preposition from.
Normally relative infinitive clauses don't use relative pronouns:
- He is the man to see.
- He is the man to do it.
- *He is the man whom to see.
- *He is the man who to do it.
but when a preposition is Pied-piped along with its object, there must be a relative pronoun to serve as the object, even with a relative infinitive.
- He is the man with whom to talk.
However, Pied-piping is never obligatory, and the preposition can be left at the end of the clause.
- He is the man to talk with.
If you try to use a relative pronoun without pied-piping the preposition, or vice versa, there are problems.
- *He is the man whom to talk with.
- *He is the man with to talk.
So, from which to gain the nation is just a fancier way to say to gain the nation from.
However, to gain the forthcoming desirable nation is a terrible clause. It seems to have been translated literally using a non-English (Turkish?) idiom or metaphor. It's not clear what it means, unless it's code for some political maneuverings.