Proper GTK environment without desktop environment

Question

I'm using Xmonad on archlinux, without a desktop environment installed. I managed to set the Numix theme for GTK2 with this ~/.gtkrc-2.0

gtk-icon-theme-name="Numix"
gtk-theme-name="Numix"

and GTK3 with export GTK_THEME=Numix in my ~/.xinitrc. For some reason setting it in ~/.config/gtk-3.0/settings.ini didn't work:

[Settings]
gtk-icon-theme-name = "Numix"
gtk-theme-name = "Numix"
gtk-font-name = "DejaVu Sans 10"

So, how can I get GTK to load the config file?

And, in general, what are things that a desktop environment sets up (like environment variables, config files, or even daemons) that GTK applications usually rely on?

That is, other than display and window managers, and a set of applications, what, if any, "glue" functionality does a DE like GNOME provide?

Thanks.