Thanks a lot, Theov!

Will do as you say. I'm at war now because I have no iron and my neighbour have two sources, so I need to grab that. But what do you think of building libraries? Should I build them in every city or just in one or two?
I think you're doing things right, but you're doing 3 things at the same time.
Are you building your empire? Ok. Do that. You will need an aqueduct and a courthouse. Want war?
Then go to war and make sure you are building enough armies for when your current guys fall.
Want to colonize that other island? Make settlers and workers.
.
Commerce = money + science.
So every coin that goes to science, is a coin that does not go to the treasure chest.
But if you have less spending
or more income, you can have more science.
Libraries add 50% of your beakers in that city. They require 1 maintenance. So a city needs to make at least 4 beakers for it to make much sense to build a library.
Marketplaces do the same (only then for cash income) but they also make people happier when you have luxuries. So I build marketplaces first. Then libraries.
Remember, if you want more science, you can also increase income and adjust the slider towards science.
I build libraries normally when I have about 6 science beakers in a city and a granary, marketplace (temple, aqueduct) is built.
oh btw, do you have that 4000bc savegame somewhere? Look like a good map to play.
Thanks.