Why just one? Considering how Greco-Roman the Imperium is, he probably had multiple rounds. I still think the Primarchs are repurposed remnants of the Eldar Gods that were imprisoned by the Chaos Gods.
I wouldn't say Julius gave Augustus a good foundation to build off of. After Caesar's assassination the Empire, which was still a democracy at the time, was in chaos. He had to survive and win a three way civil war that included Mark Anthony with the full power of the rich province of Egypt behind him. Augustus also had to curtail a senate from regaining their power and influence in the aftermath of the civil war. Augustus, in my opinion was almost as great as Caesar himself. I know I'm glossing over so much to avoid my comment being a page long , but give Augustus/Octavian's rise to power a closer look, Augustus had to be nothing short of greatness to accomplish it.
