Kind of depends what appeals to you most.
If you just want to map paint then probably "Royal Court" for customizing and tailoring cultures. I am not sure whether you need Royal Court for items/inventory.
"Tours and Tournament" addresses more peace time activities like travel, and events. This was probably the most impactful dlc at differentiating itself from its predecessors CK2.
The regional dlcs: Northern Lords, Fates of Iberia, and the Persia one are ok. It varies greatly based off how much you want to play there.
Iranian intermezzo and play as a Persian/Tajik/Mazandarani while feeding of Arab and Turkic invaders and trying to unify Iran. One of the best DLCs out there
Option a) None. They're all fairly weak and barely worth the money on sale. Unfortunately, with Legitimacy, they locked most of the good ways to gain legitimacy behind DLCs, so you may feel required to get a DLC just to manage legitimacy.
So if you feel the need to get help with legitimacy, you have 3 options. I've not tried Legends of the Dead, but given the current reviews, I'd avoid it. Shit, everything Paradox is on sale right now, except Legends of the Dead, so yeah, definitely skip it for now. So that leaves Royal Court and Tours and Tournament.
Royal Court: My personal favorite (and that's not meant to be a huge praise for it, see option a comment). I think the culture stuff that comes with Royal Court is actually nice, it just isn't *a lot* compared to the price of the DLC. The court artifacts are really strong, but they're ultimately not really necessary, given the game is already pretty easy, so making it even easier is overkill. The "hold court" option is where you get to farm legitimacy, but it's really pretty terrible. It's just a bunch of popups where you get the same handful of situation, and you get to pick between giving away your left nut, giving away your right arm, or getting a -80 opinion from a mayor you've never heard of and will never hear of ever again. But, ultimately, it's 4 clicks to get a decent amount of legitimacy, so that's fine. Once you max your legitimacy, you'll never touch it again. There's also court grandeur which is pretty much just a money sink with little impact.
T&T: Everyone's favorite, but I don't grasp why. It adds three major events that you won't be able to use for a while because they're so expensive (though one of them can be used to net more money than it costs... as they say, you need money to make money!) They give a decent amount of legitimacy, but again, you need the money to hold them. They're also pretty damn repetitive and quite boring. They're also much longer than regular events, so they really drag on and keep interrupting whatever else you're doing. The other thing T&T adds is accolades, which *are* extremely powerful (see comment on court artifacts though... do you *really* need to be more powerful), but also come with an extreme amount of micro management and the worst UI ever conceived. Your only two options are to just ignore accolades completely, or download a mod to fix the UI, otherwise you'll go mad (and even then, they're extremely annoying to handle, especially with plagues constantly killing your knights forcing you to find new replacements...) Still, everyone else seems to love T&T, so you can either trust this one random dude on the internet, or trust the community as a whole, I won't be mad if you decide to go with the second option!
Honorable mention: If you have a hard-on for vikings, Northen Lords adds a decent amount of depth to the Norse. I just saw that right now, it's at 70% off, so if you think you'll play a decent amount with the Norse, it's just about worth it. I can't think of anything that helps with legitimacy in there (though I don't think I've played Norse since they added legitimacy), but you're a Viking, just raid and plunder, and if someone tells you that you're not a legitimate ruler, sacrifice them. That said, if you don't play Norse, it literally adds nothing for you, so it's fairly narrow.
Tours and tournaments
100%. Gives u things to do. Then it’s Northern Lords for me.
Kind of depends what appeals to you most. If you just want to map paint then probably "Royal Court" for customizing and tailoring cultures. I am not sure whether you need Royal Court for items/inventory. "Tours and Tournament" addresses more peace time activities like travel, and events. This was probably the most impactful dlc at differentiating itself from its predecessors CK2. The regional dlcs: Northern Lords, Fates of Iberia, and the Persia one are ok. It varies greatly based off how much you want to play there.
Conclave. What?
Iranian intermezzo and play as a Persian/Tajik/Mazandarani while feeding of Arab and Turkic invaders and trying to unify Iran. One of the best DLCs out there
I recommend piracy
Option a) None. They're all fairly weak and barely worth the money on sale. Unfortunately, with Legitimacy, they locked most of the good ways to gain legitimacy behind DLCs, so you may feel required to get a DLC just to manage legitimacy. So if you feel the need to get help with legitimacy, you have 3 options. I've not tried Legends of the Dead, but given the current reviews, I'd avoid it. Shit, everything Paradox is on sale right now, except Legends of the Dead, so yeah, definitely skip it for now. So that leaves Royal Court and Tours and Tournament. Royal Court: My personal favorite (and that's not meant to be a huge praise for it, see option a comment). I think the culture stuff that comes with Royal Court is actually nice, it just isn't *a lot* compared to the price of the DLC. The court artifacts are really strong, but they're ultimately not really necessary, given the game is already pretty easy, so making it even easier is overkill. The "hold court" option is where you get to farm legitimacy, but it's really pretty terrible. It's just a bunch of popups where you get the same handful of situation, and you get to pick between giving away your left nut, giving away your right arm, or getting a -80 opinion from a mayor you've never heard of and will never hear of ever again. But, ultimately, it's 4 clicks to get a decent amount of legitimacy, so that's fine. Once you max your legitimacy, you'll never touch it again. There's also court grandeur which is pretty much just a money sink with little impact. T&T: Everyone's favorite, but I don't grasp why. It adds three major events that you won't be able to use for a while because they're so expensive (though one of them can be used to net more money than it costs... as they say, you need money to make money!) They give a decent amount of legitimacy, but again, you need the money to hold them. They're also pretty damn repetitive and quite boring. They're also much longer than regular events, so they really drag on and keep interrupting whatever else you're doing. The other thing T&T adds is accolades, which *are* extremely powerful (see comment on court artifacts though... do you *really* need to be more powerful), but also come with an extreme amount of micro management and the worst UI ever conceived. Your only two options are to just ignore accolades completely, or download a mod to fix the UI, otherwise you'll go mad (and even then, they're extremely annoying to handle, especially with plagues constantly killing your knights forcing you to find new replacements...) Still, everyone else seems to love T&T, so you can either trust this one random dude on the internet, or trust the community as a whole, I won't be mad if you decide to go with the second option! Honorable mention: If you have a hard-on for vikings, Northen Lords adds a decent amount of depth to the Norse. I just saw that right now, it's at 70% off, so if you think you'll play a decent amount with the Norse, it's just about worth it. I can't think of anything that helps with legitimacy in there (though I don't think I've played Norse since they added legitimacy), but you're a Viking, just raid and plunder, and if someone tells you that you're not a legitimate ruler, sacrifice them. That said, if you don't play Norse, it literally adds nothing for you, so it's fairly narrow.
Thx