We used a simple Debian 10 VM and showed the memory before starting docker and with no docker containers being started. The goal is to show much much memory dockerd actually uses.
The VM was using 58M of RAM.
it was using 99MB of RAM.
It's not scientific but fair to say dockerd itself uses about 41MB of RAM (99-58).
This proves that docker has very low requirements and doesn't have much overhead to even run containers.