Rather than worrying about settings for the AI, you might consider imposing limits on yourself that force you to play in ways that are different from your normal style.
Pick a victory style ahead of time, and only go for that one.
If you normally get a religion, don't allow yourself to do so.
Limit the number of cities you are allowed to have at one time, or never allow yourself to declare war on an AI.
Not only will things like this make the game more difficult, but they often get you to explore parts of the game that you don't generally pay attention to, which can be fun and interesting.
gaming.stackexchange.com/users/341/bwarner
You could play multiplayer, since the AIs will never be as good as a skilled human.
You could modify the AI personalities to make them more effective (give them more focus on science) and you could just play 2v1 against AI opponents.
You could also choose intentionally weak civs for a map, like playing Polynesia on a landlocked map.
gaming.stackexchange.com/users/26042/Lawton
AI difficulty settings don't really help much.
The AI is actually quite stupid, and the higher settings simply add more cheats to it, which usually only results in adding frustration, rather than challenge.
However, if you're not against using mods, try the Smart AI mod.
It's mostly just a bunch of tweaks, but it helps a bit.
You can get the mod through the Steam Workshop here: http://steamcommunity.com/sharedfiles/filedetails/?id=233424615
gaming.stackexchange.com/users/71115/Luaan
There are a few ways..
I'll go through a few: 1)
Play versus Human players
For large strategy games like this, AI will always be flawed.
Nothing is more challenging than playing against actual human players that can adapt to your strategies.
Play with friends, or try joining/creating a lobby..
usually there are at least a few games going on.
2) Don't use tricks If you want to win via science, culture, or diplomacy..
it's almost a guaranteed victory if you make everyone happy (so they don't go to war with you).
If you don't use tricks to make them happy (ex: giving 1 gold per turn to each civ), they'll be more interested in going to war with you.
Stop using these cheap tricks!
3) Try conquest Conquest is harder than other strategies, especially if you start off conquering early in the game.
4) Don't play maps with a lot of water
The AI is especially retarded when it comes to the sea...
they never buy a fleet (except for maybe Elizabeth), and their tactics
when attacking through sea is so easy to overcome... play large land maps against the AI.
5) Limit yourself
I don't like using this option because it means you're purposely doing something you wouldn't normally do... but try playing a game by limiting yourself in some way..
examples: Play the game with only one city. Play the game without diplomacy (don't even accept embassies).
Play the game with all AI players on teams.
Use bad civs.
etc...
gaming.stackexchange.com/users/80197/Othya
There's a lot of self-imposed requirements you can follow: Kill your warrior upon start - not fun with raging barbarians Build every wonder
Pick some fights at inappropriate times (e.g. right when you start on the Pyramids)
Downside of this is that it's deteriorating your perfect, big game strategy, but it is fun regardless!
gaming.stackexchange.com/users/51300/andrewb
I think the best challenge is to play against actual humans.
It would be best to play multiplayer with steam friends though.
Just going to the multiplayer lobby and joining a game might make it too difficult to actually start a game, much less get a game going past 100 turns.
Multiplayer could then all play on deity level with raging barbarians, low resources and no start bias.
This is also another reason why you should play with steam friends you know, since random players might leave if the game is too tough.
gaming.stackexchange.com/users/46627/rsanchez1
So I’ve been trying to create a truly difficult game of Civilization. I want to test my skills. So, obviously first thing to do is put the AI on Deity, and I've ticked the box for Rampaging Barbarians.  What other settings can I play about with to make the game more difficult?
How can I make Civilization V more difficult?
gaming.stackexchange.com
<civilization-5>
gaming.stackexchange.com/questions/170775
gaming.stackexchange.com/users/36737/Jimmery
The AIs will never be good as a skilled human. The best challenge is to play against actual humans. Mods can help making the game harder, but most players prefer to compete against humans.
People recommending playing against real humans. While a user is suggesting mod usage.