Ok I will try to help you.
We are building a giant (post-)medieval city too.
The first thing you should do when you start building such a giant city is dividing it into different districts. Otherwise you will just have 500-2000 same looking houses which looks pretty boring.
Our city is or will be divided into the following districts:
Port/harbor
Arena and military district
Historical town/old town
Poor housing district
Workerquarters
Market square + Cathedral square
Townhall and courthouse square
Palace + noble housing district
Mage district (fantasy)
Its helpfull to create an own style and architecture for each district, like changing size and material of the houses, placing trees or whatever. If you dont do that, it will probably look too boring in your city, one does not notice the different districts.
If you are looking for buildings to place in a town:
Town Hall
University or Academy (schools in general)
Theatre
Arena
Worker quarters (blacksmiths, bakery, brewery, butcher, shoemaker, stonemason....there are thousand medieval jobs)
Post Office
Cathedral or Church
Abbey
Taverns
Port with ships, cranes and warehouses
Courthouse or something like a palace of justice
Gallows
Library
Opera
Fortress
Palace
Parliament
Museum
Prison
I hope this helps to get some new ideas
