Concerning the squalor issue:
I've just checked and there appear to 4 different main categories of buildings. Within these 4 there are two categories of which that'll give you the oppotunity to gain public order (as brittonia there's one alone that'll give +16 publich order). The military category gives nothing, but squalor and they all give the same (a maximum of 12 for the last building - I think it's 4/6/12). The last category is pretty much all squalor too with the exception of one.
However this may vary so do some research.
What I realized though was that the manual can be quickly entered by right clicking on a building. By right clicking on one of the main buildings (if a build spot is empty for instance).
Also if you're conquering new cities you can by an agent to convert them to your culture and as others have mentioned there is also the eddict that'll give you more public order.
So all in all I do believe we're back to what I said earlier: plan ahead.
DO NOT have one city with all kinds of buildings that each into your public order. At least not in the games current state. I do, however, believe there's a fair balance after having a quick look at the buildings although there are also other things that'll have an influence on the public order.
With that said there's also nothing wrong with destroying buildings you realize you don't need. There is no need to have 3 cities with the same military building if you only have a total of 4-5 cities. When getting a new city just destroy what you don't need and roll it into your plan: do you need food, money of soldiers and make sure there's a decent balance before you begin.
It shouldn't be too problematic once you get the hang of it, but I might also be completely wrong
