I'm by no means an experienced reviewer, but somebody wanted quick reviews for the various Stellaris DLCs, so here they are.

These first ones are the mandatory DLCs - stuff that community generally agrees major features are paywalled behind or that the game feels incomplete without. Get them one way or another, either through buying them or pirating, but get them.

Utopia: This is pretty universally agreed to be the most ‘must have’ DLC Stellaris has. Megastructures are a literal game changer, and it can be tough to imagine the game without them at times considering they’re basically the late mid-game and end-game projects. Utopia also adds the three main species ascension paths: psionics, gene-tailoring, and synthetic evolution. It also adds Hive Minds on the Empire side of things - which has always been fun and played differently enough to keep things fresh if you start to get tired of normal Empires and their disgusting opinions.

Apocalypse: Adds in the Colossus, Titan-class ships, and AI Marauders. Apocalypse has kind of fallen off in my opinion but is still kind of up there in that I think its features feel so base that plenty of people have probably forgotten what it even adds. Titans are your big-boy ships, being larger than battleships, and the Colossus is your planet killer to go around blowing up, shielding, and neutron-sweeping worlds. If you ever plan on going to war, Apocalypse is a must and ship/weapons tech quickly falls off towards the end-game without it.

Federations: Don’t be fooled by the name, Federations has a little bit of something for everybody. It was thanks to this baby we can field Juggernauts, which act as massive solitary warships and mobile shipyards, along with the actual dedicated Mega Shipyard megastructure which massively boosts your ability to mobilize for war. It also brought a whole bunch of origins for giving your empire a little more flavor, and the actual overhaul to federations makes it much more viable to play diplomatically. The Galactic Community is also about as useful as any IRL political organization, but if you can abuse your way to throwing your weight around enough it can be a nice tool for forcing the borders of your neighbors open to go address the Crisis if it spawns somewhere halfway across the galaxy where it can gorge itself on retards.

Synthetic Dawn: Technically a story pack worth getting over some actual DLC. Synthetic Dawn adds machine empires and that’s basically it. They play a lot like Hive Minds, so you can kind of decide for yourself if you want more of that after playing Utopia, but fuck you if you don’t want to. Machine Intelligences are incredibly fun, and if you’re not here for fun, they’re arguably the strongest empire type in the game if you’re a bit of a minmaxer.

Past here you're officially out of the must-have territory. Everything other than those is very optional and you should probably only get them on sale.

MegaCorp: Adds the MegaCorp government type (duh), ecumenopolis’, even more megastructures, and the slave market. MegaCorp empires are fun but by no means necessary. If you’re not playing one, there can still be some beefy boons for making nice for once, unless it’s a Criminal Syndicate, in which case you should dance on the bones of their children immediately and rush to planet crack their homeworld. Ecumenopolis’ are also really good and can be a massive blessing if used properly, but you can also pretty safely ignore them if you want. I have never used the galactic slave market once in my life no matter the playthrough and have no opinions.

Ancient Relics: You can have like 6 of those aforementioned relics in any game and each one provides a passive and active effect, which can be activated in exchange for a resource (usually unity) and a cooldown that’s there to prevent you from spamming. This is also kind of one of the more RP-orientated DLCs, but it gives you stuff to do in the mid-game which can be the most barren slog to get through.

Nemesis: Actually pretty underwhelming, tbh. But it’s worth it if you have a habit of actually making it to the end game. Becoming the crisis can give you something to do and a way to win without having to purge the entire galaxy manually and the custodianship/Imperium provides a reliable way for well-built diplomatic empires to achieve their own sort of unquestionable victory without having to go full purge. Also, espionage is fucking worthless without it. You can still espionage in vanilla, but it’s one of those Paradox features that was very clearly made for the DLC and only exists somewhat in the base game as a framework. Of the big DLCs, this one is easily the worst unless you’re constantly purging and the idea of blowing up the galaxy makes you cream yourself.

Leviathans: Guardians, enclaves, and the ability for Fallen Empires to wake up. This was the first story pack for Stellaris and you can really tell. I still consider it worth getting and honestly might even rank it above Nemesis even if it actually adds very little. The various leviathans around the universe help to pad out exploration and can give your Empire some really nice boons, no matter how you’ve actually built it, and the AI enclaves are always nice to have if you’re anything other than a devouring swarm. At $10s it’s a bit overpriced, probably more like $6 - max.

Species Packs: All are optional. If you’re getting these, it’ll come down to a matter of taste and personal preference. Now, as time’s gone on, some add traits and origins beyond the shipsets and portraits, but you don’t need any of them. For example, Humanoids is objectively worth less than Plantoids, but I would still grab it before Plantoids as I think the Humanoid shipset is one of the best in the game. Get them on sale or pirate them, but they are not worth more than $5.

(Be aware that Lithoids will be overrepresented in your games if you do decide to pick up the Lithoids pack. They look cool, yes, but all Lithoid species automatically get the Lithoid trait which lowers pop growth speed and boosts habitability. The already expansionist AI will have even less reason to avoid worlds with low habitability and make worlds in your own empire and others more appealing to Lithoid pops if you or the AI agree to a migration treaty. God help you if you have Xeno-Compatibility enabled.)

Distant Stars: Adds some new unique systems, leviathans, and the L-Gates. And honestly? Other than the L-Gates I could not fuckin tell you what this pack adds other that the Scrap Bot guardian, and that’s only because it’s in the store screenshots.

Overlord, First Contact, and Galactic Paragons: Can’t really say. I don’t have these and haven’t played with them. Just from an outsider's PoV, I’d probably pick up Overlord if you like to play Authoritarian and vassalize others. It also brings with it more megastructures and two new enclave types that can both help to supplement your forces and help you more rapidly mobilize for war, which is more of a problem around the mid-game where your Empire is starting to get expansive but you're still lacking Jump Drive technology.

First Contact and Paragons look to fall pretty neatly into the category of personal preference you grab for empire RP; First Contact will add more origins and Paragons will make leaders actually useful again as you'll get the ability to pick a new trait for them every time they level up. I should also mention that First Contact adds cloaking technology to the game, which can bring a bit more tactics and cheese to warfare outside of the tried and true method of just trying to rush choke points with your biggest fleet.