But in all honesty, I use KDE Plasma with a healthy mix of Gnome apps, because I can't stand Kmail and others.
Edit: try the dev stable.
or even if you have 4 or 2. Plasma itself uses roughly 300 megabytes of RAM.
And to "SmellyGeekBoy"s point: that's the thing that makes Linux so Linux-y. I can choose that. Or not. Or a raw command line only. Or have Plasma, Neon, Gnome, Cinnamon, LXDE, Lubuntu Next, and XFCE all installed AT THE SAME TIME. It's what you want. It's what you like. It's YOUR machine. Your desktop environment. You choose and tweak the one that suits you. No one should be able to hate or discriminate against that, it's not their desktop. So fuck'em.
Every time I've tried KDE recently, the starting RAM usage is closer to 800-900mb and it anecdotally felt laggier than Unity. (I tried KDE Neon)
I was really liking Cinnamon, but I don't know. Something just felt incomplete, and I was having odd issues that seemed to be exclusive to running Cinnamon. I switched to Plasma, and have really liked it, very much, a lot so far.