From my understanding August wasn't an Emperor formally. And if the explanation is that he was a de facto Emperor, wouldn't you start with Caesar who was even more of an autocratic leader?
I am assuming August somehow transformed Rome into an empire while during Caesar's time it was still a republic in some sense. So by what criteria do we consider August to be the first one?
You might enjoy this older answer by /u/XenophontheAthenian
Why isn't Julius Caesar styled as Emperor?
Also older answer on why Julius Caesar was not considered Emperor by /u/LegalAction
And this post outlining how Caesar never held tribunician powers by LegalAction and /u/XenophontheAthenian
Yeah, take a look at those posts, and if you have further questions, maybe ping myself or one of the others mentioned by Dinocrocodile.