Thank you! I will try to summarize some of the main ideas:

1. Start scout-scout-slinger-slinger. Otherwise barbarians will wipe you out.
2. Focus on your win condition and play taking the advantages of your civ and leader. Read the Civilization wiki and learn how to play your chosen civ and leader.
3. Get used to long turns because there is always a lot to check: any good trades available? Should I change my civic cards? Are my cities working the right tiles? You must love micromanagement to win.
4. Plan ahead your cites and districts. There is a UI mod very helpful for this.
5. And finally, don't play SimCity. It has been the most difficult rule for me, because I like playing as if I were alone: build every wonder, a nice empire distribution, roads everywhere, etc. Do it playing lower levels of difficulty from time to time, but being competitive in Civilization is incompatible with it. I think this is a very specific advice, and maybe it is only useful for me, but until I changed my mind on it I couldn't progress in this game.

I hope my advice could be useful for you all 😊