Thank you for the clarifications!

I guess the only part left before being able to play good CE is to go over my biases.

(for instance, when I see flatlands, I see cottage city, it always feels like a huge waste to farm such a location

)
@SS-18 ICBM
You'll find that prince difficulty is almost as easy as noble.
I've won most of my prince games without building almost any wonder, so you don't have to worry too much about that. I think Kremlin was an usual suspect in my Willem games, but as far as the early wonders go, you can skip them without much of a price. Also, if you're near someone such as HC, you can skip them altogether, wait for him to build some, and war him.
I've also won most of my prince games before I had understood the value of hereditary rule in this game, so you can even go for early currency rather than early monarchy, although I tend to think monarchy is important in all difficulty levels. But anyway, worker techs, then defense, then pottery, then either myst-med or poly-priest-monarchy or writing-maths or alphabet, depending on neighbours and your wish to pursue other math techs-currency-col. Going for monarchy also means you can grab the Oracle, which on prince you can get rather late, it's very rarely that the AI takes it before you. The one thing you have to keep track, in case you're reading the strategy tips of higher level players, is that you won't be able to tech trade anything early in the game, so researching alphabet yourself might be needed, if you want to trade and have trading partners available.
Anyway, prince is rather easy, you most likely don't need advice if you can already beat noble Maybe one advice would be to play as a strong leader first, to get your confidence on, but, on the strategy side...
Have fun!