I have 1451 hours playing this game. CK2 is NOT your traditional grand strategy game where the goal is to conquer the world. In fact, there is no "goal" other than those you set for yourself. Want to play as a minor Spanish king in 1066 and reconquer the penninsula from the Muslims? You can do that. Want to play as a minor German count and just hold on to your single province while keeping your dynasty alive? You can do that. Want to play as Genghis Khan and conquer India instead of the Near East? You can do that too! The popularity of CK2 is that it's a unique fusion of historical strategy with RPG and sandbox elements. If that description appeals to you, definitely get this game.

A common complaint with CK2 and other Paradox titles is you have to download DLC to unlock additional features. For example, to play as a Muslim ruler, an ruler in India, a merchant prince... You have to buy DLC to do these things. The good news, however, is that the vanilla game is fine, and you can spend many hours playing as a Catholic ruler in Western Europe to see if you like the game before you pay for the DLC. Also, the cosmetic and musical DLC is entirely optional, and a lot of the more recent DLC -- Conclave, the Reaper's Due, Monks and Mystics -- add content and mechanics that, to me, feel entirely unnecessary compared to previous ones.

I would strongly recommend getting the vanilla game, seeing if you like it, and then get these DLC when you get bored of Catholic European rulers:

Sword of Islam - Play as Muslim rulers.
Legacy of Rome - Adds flavor events and traits for the Byzantines, and adds retinues (personal troops)
The Republic - Lets you play as merchant republics such as Venice.
The Old Gods - Adds a new 867 CE start date and lets you play as 'Pagan' rulers (Vikings!)
Sons of Abraham - Adds content for Abrahamic religions, and lets you play as Jewish rulers.
Rajas of India - Adds India to the game map along with gameplay aimed at Indian rulers. Feels unfinished to me.
Way of Life - Adds more role-playing elements to the game, if that's your jam
Horse Lords - Adds more content for nomadic/tribal rulers. The Genghis Khan DLC.

Everything else I feel is less important.

I have 1451 hours playing this game. CK2 is NOT your traditional grand strategy game where the goal is to conquer the world. In fact, there is no "goal" other than those you set for yourself. Want to play as a minor Spanish king in 1066 and reconquer the penninsula from the Muslims? You can do that. Want to play as a minor German count and just hold on to your single province while keeping your dynasty alive? You can do that. Want to play as Genghis Khan and conquer India instead of the Near East? You can do that too! The popularity of CK2 is that it's a unique fusion of historical strategy with RPG and sandbox elements. If that description appeals to you, definitely get this game. A common complaint with CK2 and other Paradox titles is you have to download DLC to unlock additional features. For example, to play as a Muslim ruler, an ruler in India, a merchant prince... You have to buy DLC to do these things. The good news, however, is that the vanilla game is fine, and you can spend many hours playing as a Catholic ruler in Western Europe to see if you like the game before you pay for the DLC. Also, the cosmetic and musical DLC is entirely optional, and a lot of the more recent DLC -- Conclave, the Reaper's Due, Monks and Mystics -- add content and mechanics that, to me, feel entirely unnecessary compared to previous ones. I would strongly recommend getting the vanilla game, seeing if you like it, and then get these DLC when you get bored of Catholic European rulers: Sword of Islam - Play as Muslim rulers. Legacy of Rome - Adds flavor events and traits for the Byzantines, and adds retinues (personal troops) The Republic - Lets you play as merchant republics such as Venice. The Old Gods - Adds a new 867 CE start date and lets you play as 'Pagan' rulers (Vikings!) Sons of Abraham - Adds content for Abrahamic religions, and lets you play as Jewish rulers. Rajas of India - Adds India to the game map along with gameplay aimed at Indian rulers. Feels unfinished to me. Way of Life - Adds more role-playing elements to the game, if that's your jam Horse Lords - Adds more content for nomadic/tribal rulers. The Genghis Khan DLC. Everything else I feel is less important.