Here is my save if anybody feels like looking at it.
View attachment 325417
What should I build if I shouldn't build things that cost maintenance and I'm not going for a military victory? Should I simply build workers and wealth once I arrive at my unit limit?
I've taken a quick look at your save: Regent level, 3 other known civs, Standard map size?, continent land mass, one known continent, Accelerated Production.
If you are not going for a military victory, what VC is your goal?
You are rated as Weak to the other 3 known civs, due to mostly defensive units. Your military needs to be strong enough to prevent a war, not just defend the land after it is attacked. That won't prevent the AI from being stupid, but it helps.
Why is Bactra bulding Palace? That will make a size 5 city have 0% corruption instead of the current capital, which is at size 8.
Each city has 21 tiles it can work. However, it takes learning Sanitation, an optional tech, before you can build hospitals that will let your cities grow to size 21. That tech is a full age away. So while Persepolis will be able to work 21 tiles at some point in the future, the most it can work for the next 50 turns or so is 8 to 12 tiles. Or to rephrase it, off the 21 tiles that Persepolis can work, nine of them will not be worked for another age and are not doing you any good.
Because of this, most players here place their cities much closer and let them max out at size 12. Closer tends to be City-space-space-city which also allows foot units to move from city to city in one turn, once roads have been laid.
For 17 cities you have 9 workers. Not enough workers. Even as an IND civ and those faster workers, you still need a 1 worker per 1 city ratio.
It is late for me so I hope this doesn't sound snappish or put-downish. It is meant to instructive, not destructive.
However, as timerover51 said, play the game the way you prefer to and enjoy it. Listen, ask questions and learn and then decide how/if to implement what you have learned.