That looks like you have scattered data. If you have an array of latitudes, an array of longitudes, and a corresponding array of some values z, then the easiest way to make that kind of plot is to treat longitude as the x variable and latitude as the y variable. Then use the standard scatter function like this:
The 50 above sets the size of the markers. The word 'filled' makes the circles filled with color rather than hollow.
If you would like to add national borders, I recommend using the borders function in Climate Data Toolbox. Syntax would be
to plot the outline of national boundaries.