OpenStreetMaps (OSM) maps are free to use, because they are created and edited by the community. You can update and contribute to the maps here: http://www.openstreetmap.org
There are a lot of sites that help you download an specific area/country and convert it to Garmin format (.img).
The places I've used are:
http://garmin.openstreetmap.nl/
It give options to select specific parts of the world or a part of a country. If you choose other than a hole country, my experience is that I have to wait at least a week to get the file ready for download. If I choose a country, then it is instant.
On the above sites you get a zip file. Uncompress it and save it. If you would like to be able to remember where you got the file and what date it was created on the site, build a folder structure of your choice. An example to the right.
It can also be good to rename the file in the same manner. In my file name I also keep track of what 'Typ-file' that is included. More of that on another page.
Note that the file name is not what is visible on the watch in the list of maps, e g when selecting what maps that you would like to view.
The name that shows up in watch menu is a parameter in the file. You can use the tool 'GMapToolSetup0932.exe' to change that. That is also going to be described in another page.
Copy the .img-file to your Garmin folder on watch.
You configure per watch app, what maps are going to viewed.
To choose that the new map will be viewed on watch: