The best the way to start drawing your map is to look up reference images of the object you’re trying to build (in your case a city).
Once you find some buildings you like, map a general layout of the city. Do you want it in a circular shape? Square? Etc.
Draw a few quick designs and begin building the basic shapes, position them how you want, and then get into the details (materials, decorations, colors, windows, scenery, etc).
Keeping a list of what you want to do every day helps. Break each step into smaller, more manageable chunks.
Hope this helps!
Always start by noting your ideas down first and then draw the map.
Where is it located? What type of environment is it?
What structures would you include? (Buildings, huts, cabins, etc)
What ideal style are you moving towards? (Old structues, modern, etc)
What is the purpose of the game? (Roleplay, adventures, etc)
Once you have listed all the following, you can start planning out your city, if you ever end up getting stuck, don’t be afraid to search the internet for ideas, try not to completely copy photos.