The guide was written to be applied when playing online 4x4 Multiplayer Tournment (MPT). Refer to the Guide below for a brief intro on how it works:

https://steamhost.cn/steamcommunity_com/sharedfiles/filedetails/?id=1669107567

I basically run the game on hotseat twice, controlling 4 civs in MPT:

Babylon, who had a standard start point with bonus grasslands and forests.
Greece, who did not have any forest and had food plain.
Hitites, a industrious civ with a standard start point but without forests and;
Iroquois, a agri civ with a standard start point (with rivers).

I played each game equally for 25 turns, and used the following methodology:

(i) Capital would build warriors until city is 3 turns to size 3. THen it would build Settlers.
(ii) Granaries would be poprushed.
(iii) All other cities would warriors until the city can support a worker.

For Babylon, I chopped a forest to speed up granary. Did not do this for the other civs.

I let AI choose which tech I would research and I set all units out to explore on automatic.

Those were the start points:

After 25 turns, those were the results:

The green cells highlight where one methodology clearly beat the other.

This is how each game looked like - with the first image being the "build Granary first" strategy and the second "building a 2nd city first".

Generally speaking, building granary first will allow a faster expansion and more units compared to building your 2nd city before Granary.

On the other hand, building the 2nd city first allows you to improve your land faster.

As a rule, I would recommend you to always build granary first unless you want to hook resources ASAP (example, when playing with Egypt) or when improving your land is a must (plains, floodplains or if it lack bonus grasslands).