Apply these USE flags before emerging Qtile:
echo x11-libs/cairo X glib opengl svg >> /etc/portage/package.use/qtile
Then emerge Qtile:
emerge --ask x11-wm/qtile
Qtile currently has no package-specific USE flags.
Qtile can be customized by editing the config file in ~/.config/qtile/config.py. This file is generated when there is no present configuration file. If Qtile is running while configuring it, restart Qtile using its default keybind, Super+Ctrl+Q to apply changes.
The default configuration file can be found at https://github.com/qtile/qtile/blob/master/libqtile/resources/default_config.py.
To check if the changes are written correctly:
python3 -m py_compile ~/.config/qtile/config.py