I understand you may be looking for an exegesis that fits within your existing view ('that 90% of the Book of Revelations is yet to be fulfilled'). However, I will be offering a more text-critical approach.
In AD 70 the Roman Empire destroyed Jerusalem and its temple. Within a couple of decades, Jewish authors began comparing the event to the first destruction of Jerusalem and its temple by Babylon in 587 BC. In fact, some of John's contemporaries called Rome by the name 'Babylon' to make this identification explicit.1
Accordingly, most scholars understand the name 'Babylon' in the Revelation to be symbolic for the city of Rome. John further identifies Babylon as 'the great city' which is seated on 'seven mountains'. Again, most scholars see this as a deliberate reference to Rome's nickname as 'the city of the seven hills'.2
Revelation 18 is thus understood as a lament for the downfall of Rome, with John inspired by the style of Ezekiel 26-28; specifically, John writes about the city's downfall from the perspective of very people who prospered by Rome's violence and wealth. These are the merchants whom John mentions.
The 'magic spell' (other translations say 'sorcery' or 'enchantments') is the word φαρμακεια (from which we get the word 'pharmacy'), which literally refers to some form of 'drug magic'. It could be used for magic-based potions, poisons, or even medicine.
Because John says this φαρμακεια is the manner by which Rome deceived the nations, he may be referring back to the 'wine of her sexual immorality', mentioned in Revelation 14.8 and 17.2ff. She has made the nations drunk on her wine, and led them in the persecution of God's people.
1 1 Peter 5.13; 4 Ezra 3.1-2,28-31; 2 Baruch 10.1–3; 11.1; 67.7; Sibylline Oracles 5.180-201
2 Cicero to Atticus 6.5; Georgics 2.534-535; Aeneid 6.781-783; Elegies 3.11.55-57; Tristia 5.69; Epigrams 4.64; Sibylline Oracles 2.19; 11.145-154; 13.61; 14.138