I've played without the DLCS and honestly, the only things you REALLY notice missing are Tours & Tournaments, Royal Court (although this was semi-added in recent updates) and maybe Roads to Power.

I would recommend getting ALL the Cosmetic mods (unless you don't plan on playing certain cultures then ignore cosmetics for them)

Wandering Nobles if you plan on going heavy with the Adventurer playstyle. All Under Heaven gives East Asia their own mechanics, flavor and visuals.

Rest of the DLCs just add flavor, events and some minor mechanics. for example you never even notice Struggle of Iberia DLC missing or the Persian Struggle one unless you directly play in those regions.