There is no comprehensive guide because it’s too complex. I remember reading a really good civ V guide because it was a little more linear in approach.
I found just playing the game a bit at the start was just great and then asking questions is a good way to go.
@Buktu advice is of course sound like all advice on the forum. To me there are a few tips that really help.
1. For the first 70 turns getting your cities out is important, whether building or conquering.
2. Keep your cities together, if they are left in a place with more enemy cities closer, they are likely to change sides
3. When fighting, try to defend rather than attack, especially at the beginning. Fortifying yourself on a hill and being attacked is far better than attacking back.
4. There is a civic that gives double adjacency for a campus, getting a few good adjacency campus then using this card makes the game a lot easier to play.
5. It’s a game, first and foremost, don’t burn yourself out on it, it s something to do for fun. The game can get a bit long and dull near the end to some people. But it is still a good game.
if you are reading this from a browser you will see some guides just below that cover some key aspects.