Hello

I'm pretty new, just started a few days ago, and have read some short guides. But I've reached a point where I don't know which decision is better.

Once the empire has a capital and two or three unattached outposts, I'm not sure what to do with them, or with the first of them at least: attach the outpost to my capital, or upgrade it to a second city? I see that upgrade costs many more influence points, so likely is better, is it? Is it worth to wait until I get enough points to upgrade?

Thanks in anticipation

A second city is often worthwhile at that point in the game, it will be easier to attach new outposts to that second city than to the larger one.  However, you can get a second city by conquering an Independent People (easier option), or by taking it from another civ (harder option), because that lets you cover a bit more territory than things right next to your capital (and it doesn't cost the 160 inf for the city + ?? inf for the outpost to start.

Thanks for your answer. Indeed I was thinking to choose that, upgrade to have a second city, although I'm always short of influence points.

About conquering independent people, that seems fine but I haven't met any of them yet, perhaps I haven't explored enough.

My suggestion would be to always attach 1 outpost to your first city and then make your second city and attach 1 outpost to it as well. The reason being attaching just 1 outpost is incredibly cheap. I usually don't attach more than 1 outpost until much later in the game, since the influence cost gets pretty insane.

In the beginning of the game both options could be useful. In fact you need both, the question is the order. 

You need 2 (or even 3) cities, as it is how much you City Cap allows atm.

But you need at least 1 (or 2) ouposts attached to every city to increase their starting outputs

In the late game you don't need attaching new territories unless you finish developing the current one. They don't give much, but increase the costs.

Attaching new territories can help a lot for certain EQ.

this is one of the puzzles that make the game interesting and a valid answer for a specific situation may not be so for another

in the current ruleset, i usually go for 3 early cities with only one attached territory for each one. i only go for a second attach towards the end of ancient when there isn't much left to do before jumping eras. now, this is when playing the typical map in which a lot of land is available and it will not work at all in archipelago style layouts, for instance

the main plaza of a city has some early bonuses that are very powerful, such as the effect of civics and religion

Okay, I don't know if for good luck or intuition, but I did what later have read here. Now I have two cities, with an outpost attached to each one. And likely I'll keep this status for a time, expansion is now harder because independent people has appeared and established around my territories. I must say that I'm hooked to this game, and playing more hours than I should, haha.