As the name says it, I wanna suggest Netrunner Rolling, minimal or basic edition. Including the bare minimal packages, no games or extra software, like office suites, or so, using the open graphics driver. Just the essential base. What do you think?
I agree, I used a manjaro minimal testbuild iso for this and switched it back to the stable repo. Boots up at 380 mb Ram.
https://sourceforge.net/projects/manjarotest/files/16.06-dev/kde/minimal/