I formulated a small guide for rapid expansion here: Civ VI early game guide for the Decidedly Average (feedback welcome!)
You can also read my post here, where I settled 23 cities (iirc) peacefully without even being declared on (it is a large map though): Benchmarks Thread: Compare your T100 stats!
If you want you can try out the map, the t1 save is attached! It has room for probably settling 30 cities. It was my first time ever playing Greece and my third or fourth game in GS so you should have no problem getting to my benchmarks
I would recommend you to first try out the Early Empire rush strategy, because that way you get your cities out and online the fastest! If you feel comfortable with that you can use the ancestral hall strat.
On a related note, it seems I completely forgot to post about my Rome game here, what a shame! I will just copy paste my other post and add the T100 benchmarks:
I finished SV on Turn 184 with Rome.
Not on Hall of Fame settings at all, just playing a game on my preferred ones.
Large map / 20 CS / one less enemy Civ / Standard Speed / Lakes (obviously cooked settings!)
Here you can see my T100 benchmark. Science and Culture is decent but not amazing. GPT is good. Faith and TR are abysmal!
I killed two AIs this game which is why I have so many cities but such bad relations. This was also an Ancestral Hall game.
Victory screenshot (well, one turn before actually). I was very unlucky in almost every regard: unlucky with chops and having too little aluminum/not planning energy in my chop city, capital had abysmal production so I set up another space-port city, also of course the last hidden tech was the one I needed
couldve been a sub T17x victory for sure but oh well!
the map seemed insane at first but turned out to be mostly okay. I could have settled like 30 cities here, but I think I would've finished slower. The land is not that good. So much free space, but I don't think it would've been worth it. Even some of my cities were just straight up bad, like they only had one or two good production tiles. I think I really pushed the boundary of how many cities you should settle in my last 2 games. Settling ~15 cities and then focussing on military seems like a better strat.
Short writeup, will do a more detailed one in the benchmarks thread:
Got forward settled by scotland twice. Forward settled them in return, then got the settler pantheon. After Ancestral Hall I spammed settlers forever. I went Dark age into Heroic which was amazing. Settled I think 16 or 17 cities (I think 22 in total, but please count if you want to, minimap is there!
). I got these wonders in the following order: Pyramids, Angkor Wat, Mausoleum, missed Forbidden by 3 turns, Potala, Ruhr, Oxford, Big Ben, Amundsen. Focussed on science the majority of the game and should have put a little more into culture. Rome bonus is not enough to foregore theatre squares, especially after ~t120 culture went very slow. In the end though most things worked out pretty beautifully. I took out the scots clean, took out england clean, and took 3 korean cities and pillaged them in the late game. I think pillage wars are incredibly and can shave off 5-10 turns depending on the intensity.