I haven't played this game for quite a while and am now coming back to start a new game.
As there has been a lot of DLC released in the meanwhile I'm wondering what is the most important to get. I've every single piece of DLC sans these:
- Conclave
- Horse Lords
- Way of Life
- Charlemagne
Which of these enhance the experience of the base game if i want to just play Christians/Vikings?
The main point of Horse Lords is playing a a steppe nomad so if you're not going to do that, there is no point in getting the DLC.
Charlemagne gives you a new start date (769 AD), the ability to grant titles as viceroyalties (which means you are the heir), and the ability to create a custom titular kingdom if you own 3 duchies or a custom titular empire if you own 3 kingdoms. It's nice, but far from essential.
Way of Life allows you to choose a "focus" for your character such as Hunting, Seduction, or Business. There are 10 available and when you pick one you get related events, some of which will slowly "level up" your character in that focus. Once you level up the focus all the way you get a lifestyle trait that grants 3 attributes points and something extra. Examples of lifestyle traits are Hedonist, Master Seducer, Duelist, Scholar, Gardener, Impaler, etc. The main complain people have about WoL are the Seduction and Intrigue foci, because AI characters that take them sort of run wild with them and use them indiscriminately. For seduction that's mostly an annoyance (you can never be sure that your children are truly your own), but Intrigue can be quite serious because you can get kidnapped by a vassal who likes you and die during the attempt. I'm not entirely sure how common that is since I don't have it. But I'm sure others will be more than happy to give you their impression.
Finally, Conclave is the only one that I actually consider essential. That's because some features of the free patch are actually incomplete without it. For example, you can use favors to work a way around defensive pacts that form against you, but you need to have Conclave in order to enable favours in the first place. Aside from that you get the new council mechanics and the new child education.
So I would recommend you to get Conclave and then consider Way of Life as it complements the new education system.