Hello, d.miller! I am also somewhat new to the Art of Memory but here is my suggestion if it makes sense for you:
I remember short lists via small palaces. Rest stops, a park, gas stations, and the like all work very well. I simply choose one that is mostly empty (fewer distractions) then walk through it a few times to develop the layout, followed by conceptualization of a path and then I walk the path backwards and forwards (at least 4 times going through the entire place) while also walking it in my head making sure it works, then I purposefully distract myself with a lunch break or a couple songs or something and then mentally walk through the palace again and repeat the path in real life to concrete it in my memory.
These palaces usually hold between 1 and 10 loci depending on how big it is, how unique the loci are (multiple corners is a no-go for me, for example), and how many people were around (more people around when creating palace = less loci).
I split my micro palaces up and then grouped them and placed them in specific palaces to hold the journey. So the first year I went on vacation to Colorado and Yellowstone and my favorite place to stay was a campground in Utah. So in that campground I start by placing a Bison in the first loci because it was the most notable animal I saw that trip and I consecutively place a link to each rest stop like normal loci. Second trip to Colorado and Yellowstone the palace is signified by a bear, most notable place was a hotel in Deadwood. The third palace is signified by a cougar and is a place in Denver; the fourth a moose in a place in Dillon.
I organize them like this so that I have a specific cycle of places so I don’t keep reusing the same ones or forget which palace I connect to to continue the information stream. The same concept could be used in a single city as businesses on a specific street as one group of micro-loci.
As far as scholastic information such as you posted such as “the reasons Rome fell” you don’t necessarily need a palace or a journey, simply the image of what is happening.
You could create a mental image of Rome (I imagine a building with massive columns) and then tell a story to explain why it fell. So I imagine Rome surrounded by a massive wall with barbarians banging on the north wall. Owls are flying secret messages in and out of Rome with various stamps etched into the wax seals of the letters. A man in luxurious purple robes is carting out a load of gold, and inside the building is many other individuals in equally nice robes that represent Roman upper class, as well as some dark-cloaked stealthy figures dotted around who clearly are friends with the Upper Class. Each dark-cloaked individual is doing something shady from bribes, to sawing table and chair legs, stealing food, and whipping the slaves of the Upper Class; many also hold cups of poison, knives, and a book that represents Knowledge in my mind. There are several treaties with symbols that represent various city-states and several of them are on fire or signed by a dark-cloaked man, who has no authority to sign a treaty.