In between Iamblichus and Proclus, you should get the Aclepius translated either by Clement Salaman or Brian Copenhaver. Do not get Taylor's version of Apuleius as he censored the naughty bits, though his does contain On the God of Socrates and On the Platonic Philosophy. My prefered translation of The Golden Ass is by Joel C. Riel.
For Pythagoreanism, which plays a vital role in post-Iamblichean Neoplatonism, we have few sources left. The most important is the Introduction to Arithmetic by Nicomachus of Geresa, who inspired Iamblichus to take up the banner of Pythagoras and of whom Proclus considered himself a reincarnation of. This treatise was translated and improved upon by Boethius in his De Institutione Arithmetica, translated by Michael Masi in his Boethian Number Theory. The Theology of Arithmetic mentioned before can get quite heavy – read either of these or both before. Another valuable treatise is Mathematics Useful for Understanding Plato by Theon of Smyrna, which deals with arithmetic, music and astronomy.
Julian the Emperor was an avid admirer of Iamblichus. It is believed that he commisioned an introductory treatise, which was written by Sallustius. It goes by various names, but the edition I have is called On the Gods and the Universe by Arthur Darby Knock and explores the various possible sources for the doctrines contained therein.
For Proclus, all by Taylor, start with the Elements of Theology. Essays and Fragments contains many interesting musings, but most importantly The Life of Proclus by his student Marinus. Most of his remaining commentaries on the Alcibiades, Republic, Timaeus, Parmenides and Cratylus are included in Taylor's five volume edition, but I'd recommend skipping them until you have Plotinus, Porphyry and Iamblichus under your belt. The vast majority of the fragmented Chaldean Oracles is from his Timaeus, issued as a seperate two volume set, and his magnum opus, The Theology of Plato. You can get the fragments out of context in Ruth Majerick's edition or read them in the context of Proclus.
For Middle Platonism, there is the Handbook of Alcinous, the Moralia and Lives of Plutarch, various works of Apuleius and fragments from Numenius of Apamea, the latter also being issued by Prometheus Trust.
Both Taylor's translation of Plato and Aristotle contains the commentaries of various post-Iamblichean Neoplatonists: Julian, Olympiodorus, Syrianus, Hermias, Simplicius and Damascius, the latter being the last head of the Platonic Academy before it was shut down for good by Justinian. His treatise, Doubts and Solutions Concerning First Principles, has been translated by Sara Rappe.