Please don't bother with Civilization 6. Get Civilization 5 and the expansions, then get Vox Populi.
https://www.vice.com/en_us/article/ez34jp/the-modders-who-de...
https://civ-5-cbp.fandom.com/wiki/Civ5_CBP_Wikia
Civ 6 is just so bad in comparison.
Some things are up to personal taste, like the graphics and art style. I definitely prefer how Civ 5 looks.
There's also the fact that Civ 5 was primarily designed and developed as a desktop PC game, while Civ 6 was designed as cross-platform (desktop, tablets, consoles, and smartphones). Some people will prefer that too, though.
But there are major differences that aren't up for discussion:
Civ5 has better mods because Firaxis exposed/released APIs that give modders more control/access than Civ6 provides. This means more & better mods.
VP has better AI than Civ 6. I think it has some of the best AI in the history of gaming.
VP has better balancing, for both civs/leaders and tech/social.
VP has an active developer who releases frequently and listens to community feedback. More importantly, VP's developer primarily cares about making the game fun. Firaxis primarily cares about squeezing money out of customers through expansions and DLC.
I really regret buying Civ6. I even got suckered twice with the expansions, thinking they would at least lead to modders bringing the game up to par. Nope.
I have 1000 hours in Civ 5 (mostly Vox Populi), and ~100 in Civ 6. Those hours in Civ6 have been in 5-hour bouts of me trying to enjoy the game, then giving up because it feels so bad to play.
I wish Firaxis would just hire the guy behind VP and put him in charge of the series.