Improve your empire internally
Leviathans gives you many additional options to "build tall". More state and province level options have been added, Monuments, which are historial structures in the world, give unique bonuses for owning repairing/improving them. More options to spend your admin points on infrastructure which gives tons of bonuses and makes building up smaller nations alot more fun in my opinion. If you like more internal management or starting off as smaller nations, would recommend this DLC.