Simcity... this could be very difficult.
You have to play around with tilemaps.
Imagine left click set a tile to a road tile.
What if a road has intersection, does it have to be set to a T-shaped intersection or + shaped intersection? You need events to take care of all these.
For people going from one place to another, they must be able to know their shortest path. There is pathfinding feature in C2:
But before I overwhelm you further, could you please try create a simple program first where:
1. There is a road with several intersections.
2. A person walks from point A to point B on the road.
Try do the above first before proceeding any further. If you need help on specific features, create new topics for those.