If you have a site next to a river, and there's no water in any other direction, chances are it will slope down towards the river. It's kind of how rivers form and why they flow where they do.
Building up a water reservoir is generally a good idea. Preferably several for safety and redundancy. And you probably want it above the site so you can later direct that water where you want. It should also let water into the groundwater.
Gravel doesn't cause a road to get muddy. As long as you keep it from being washed away, it's pretty good against rain. With time you get stuff mixed into it that can make it muddy, though.
Yeah, good roads is like classic Roman technology level, at most. Probably earlier, depending a little. It's more a matter of manpower than technology.
For roads, you don't need pedestrian paths on both sides. You only need that on streets inside cities and towns where you have shops and stuff you want to access directly from the street.
So magic can be used by anyone as long as they know how, including writing those things in the first place. That seems like knowledge they would benefit from spreading.
She reminds me of a certain Silent Witch.
"Able to understand the concept of zero."
That's... not a high bar. That concept was known by the ancient Egyptians and several other ancient cultures. A lot of them didn't have a specific symbol for it, but that didn't mean they didn't understand it. They might not have had a positional system in their specific culture, but that's a slightly different idea.
They...
don't have a law for practicing voodoo?