Very good and deep game.
Especially the trade system and the random building options are great.

I try to keep this updated by rating the nations i played in terms of difficulty and fun from 1 to 5

Original campaign

Rome
Difficulty 2 (beginner)
Fun 5 (roflstompf)

Sparta
Difficulty 4
Fun 4

DLC campaign
Athens
Difficulty 3
Fun 5

The DLC adds a lot of cool new mechanics like the rivalry between athens and sparta, new buildings, perks and impediments for regions and regional decisions.
I like the shorter campaign.

Wishes for futute patches /dlc:
Smaller map
QoL features to reduce micromanagement in the mid and endgame
More possibilities to influence the government and the leader