I dont sure if it has an existing one, so here is my guide for this
Rome-octavian
Well, much cities for you, but you will be fighting antony, another big nation lol.
This is divided into four fronts:
namnetes
nervii
iberia
main front (rome-antony)
This one is easy, you just have to save up money for more allies, to do easy work.
for namnetes and nervii, dont attack namnetes, but attack nervii. Push through it and go for the other one. Use your economy, primarily on this front (at first).
in iberia, use the army near there to claim cities there. Then, when the push on upper gallia finished, use your economy then to push through it and save your friend Lepidus from losing cities.
for the main front, use only the troops near there including octavian and troops near him. Push into his cities one by one, and use octavian for wrecking cities there. Beware, you have only a limited troops pushing there, but after the other fronts cleared, just spam cav inf and archers to destroy antony. After that, it is only easy conquest, as your allies are also doing their works assisting you for other cities.
clean up: you’ll have to go to africa to finish antony, so use this oppoutunity to clean africa and asia.
remember i said to save up money? Well you will use the saved money to make other neutral nations to be your allies. (300 per nation, per turn).
p.s. You can say that it is useless lol.