>>24976428
The primary ancient source for the specific curriculum/reading order of Plato’s dialogues attributed to Iamblichus is not found directly in the extant works of Iamblichus himself, but in a later text known as the Anonymous Prolegomena to Platonic Philosophy, a late ancient (6th-century CE) introduction to Plato’s works that preserves this tradition.
Stanford Encyclopedia of Philosophy
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Key Source for Iamblichus’s Platonic Curriculum

Anonymous Prolegomena to Platonic Philosophy

This is a late antique, anonymous Greek text (often attributed to a sixth-century Neoplatonist in the school of Olympiodorus the Younger) that preserves the reading order of Plato’s dialogues ascribed to Iamblichus.
Stanford Encyclopedia of Philosophy
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In this text (chapter 26 in the edition of Leendert G. Westerink), a list of twelve Platonic dialogues is given, described as offering a systematic overview of Plato’s philosophy — a canonical curriculum rooted in Iamblichus’s teaching tradition.
Stanford Encyclopedia of Philosophy

Important Note:
Iamblichus’s own writings don’t survive in full, and no extant work by him explicitly outlines this curriculum in his own hand. Our knowledge of the curriculum comes from later Neoplatonic documents that ascribe the sequence to him.
New World Encyclopedia
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What the Anonymous Prolegomena Attributes to Iamblichus

According to the Prolegomena, Iamblichus’s reading order began with introductory and ethically oriented dialogues and progressed toward more theological and philosophical depth:
Stanford Encyclopedia of Philosophy
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Alcibiades I

Gorgias

Phaedo

Cratylus

Theaetetus

Sophist

Statesman

Phaedrus

Symposium

Philebus
…and two “perfect” summative dialogues:

Timaeus

Parmenides
Patreon

This sequence was understood as a systematic pedagogical progression through Plato’s doctrine, arranged for moral and philosophical development rather than by Plato’s own chronological order.
OUP Academic

Modern Editions of the Source

If you want to read the text itself (in Greek or in translation), the key modern edition is:

L. G. Westerink, Anonymous Prolegomena to Platonic Philosophy — this is the standard scholarly Greek edition with commentary and sometimes an English translation of the relevant sections.

>>24976428
The curricula actually vary a bit, but the AI slop here >>24976457 is mostly right.

The thing is, you're supposed to have run through the Aristotleian corpus before the first Platonic dialogue. Things like Porphyry's Isogogue and commentaries on Aristotle might be consulted around this point. The Prolegomena would often be read first though.

However, from what I've seen the Philebus is often last.

They also thought you should read all of Aristotle first