I personally spent about two weeks studying the game before actually playing, which was rather annoying.
I think the game is still too new to have a comprehensive guide. If you have a few dozen hours to spend before actually playing, you could read through all the "quick questions and answers" thread. Otherwise, I'd just watch through 2 or 3 Let's Plays on Youtube, preferably by different players.
As another CIv5 deity pro just starting out in this game, my quick tips are:
1.) CIv5 was about tall, narrow empires. This game is about wide, short empires.
2.) It may be a hard pill to swallow, but we were pros at civ5 but new to this game. Even though we always won at deity for every civ game we've played in the past 5 years, we need to move down to king or emperor for a game or two to learn the basics.
3.) In Civ5, science (derived from population derived from FOOD) was the ultimate resource. In CIv6, it's the hammer.