If you want to dockerize a GeoDjango project, the most common method is to use an oficial Python image as its base, and install all GIS dependencies over it, being GDAL the heaviest one, making your final image easily reach the mark of the multi-megabytes. But GDAL is very modular, and most GeoDjango projects can work fine with its basic compilation.

This article shows how to flip that dependency, and use the official minimal GDAL images as a basis, adding the Python/Django structure over it. Also, how to pick a leaner PostGIS image to save even more space on your development environment.