First of all, there should be (optional I guess) Sandalpunk. Antikythera should go there, and for a few other ideas there is: https://en.wikipedia.org/wiki/Hero_of_Alexandria
An overview of that time: https://en.wikipedia.org/wiki/Late_Antiquity
An additional civic: https://en.wikipedia.org/wiki/Tetrarchy
For military techs: https://en.wikipedia.org/wiki/Late_Roman_army
In general, one of the most important persons of that time: https://en.wikipedia.org/wiki/Diocletian
An overview of that time: https://en.wikipedia.org/wiki/Late_Antiquity
An additional civic: https://en.wikipedia.org/wiki/Tetrarchy
For military techs: https://en.wikipedia.org/wiki/Late_Roman_army
In general, one of the most important persons of that time: https://en.wikipedia.org/wiki/Diocletian