This is how I do it:

Note: All of my 9 cities are clustered together

1 Main city (one could make two main cities for backup purposes)
3-4 Secondary cities
The rest are Tertiary cities (resource/army generating only)

Rally Point - All cities
Marketplace - Main and Secondary cities, not Tertiary cities
Embassy - Main and Secondary cities, not Tertiary cities
Feasting Hall - All cities
Inn - Main city only
Beacon Tower - All cities
Relief Station - All cities
Forge - Main city only
Workshop - Main city only
Warehouse - I do have these, but I plan on removing all of them. If someone hits me hard, I lose the city regardless of warehouses. I regen resources easily with 9 cities to recoup.

Cottages & Barracks - The remaining spaces are used by these two. I think 10 Cottages should be fine, and the rest should be Barracks.

Option:
- You can remove relief station if you feel your cities can handle themselves, and if they are right next to each other