The expansion packs (Sword of Islam, Legacy of Rome, The Old Gods) are worth it. All the cosmetic stuff (music packs, dynasty shields) are skippable.

Yep. The expansions are all fantastic, cosmetic stuff is nice for flavor but it won't hurt the game to not have it. Still for that Vikings dlc, you gotta get those beards

I honestly think the portrait packs are vital imo.

The expansions are worth it, but only get Sword of Islam if you want to play muslims and the republic if you want to play as... a republic.

Legacy of Rome is vital, and get sunset invasion if you're fine with ahistorical business.

The Old Gods, though, si the most vital of the bunch. It adds so much...

Sort of thought you were crazy for suggesting that people buy the portrait packs, but after playing a few hours of Old Gods I can see where you are coming from. Much easier to differentiate who you are dealing with, I guess.

You can't have Old Gods without them beards!

More worth it than Horse Armor, I'd say!

I know the sale has expired so this isn't super relevant, but I can definitely speak to the quality and depth of the DLC.

Sword of Islam and Old Gods both add a significant amount of gameplay and depth to the game, and to a certain extent so does the Republic. The Legacy of Rome makes playing as the Byzantine Empire a bit more unique and interesting, but doesn't add much depth to it compared to the others, and the Byzantines were never that fun to play as to start with. Sunset Invasion, take it or leave it, and as others have said, the cosmetic packs are fairly pointless, but at the same time the whole game is staring at the same map screen and portraits for the entire time, so anything that adds a bit of variety to the experience will add a lot for people that care about that stuff.

You just validated my purchase of the portrait packs and the units packs.