Following are the MB requirement of several distribution in common use.
A guy had done this in his computer probably using Ubuntu.
FreeBSD Text Console 97MB
Openbox 614MB
MATE 1361MB
XFCE 1548MB
GNOME 2622MB
KDE/Plasma 2843MB
I use Gnome exclusively and was under the impression it uses less MB than KDE.
I am proven wrong.
XFCE of Emmabantus was the safest bet for me.
Another guy has done a separate testing he is reporting under 1000Mb for all.
He probably has done on a virtual machine.
I did research in preparation of writing a book on different desktop environment.
I think it is the features that come with DE that matters not the RAM usage.
Besides, unlike my days RAM is cheap and guys playing games use 32 to 64GB RAM.
My NUC has only 8GB RAM and it is good enough to run the Virtual Machine which uses only 2 GB of RAM when running BOX utility.
What matters is the disk space allocation which needs at least 10GB space. It gets consumed running 3 of 4GB Isos.