This is a vimrc and colour scheme which works well for me on PortableApps gVimPortable on Windows.
$HOME
= gVimPortable/Data/settings
Place _vimrc
at $HOME
Place gruvbox.vim
at $HOME/vimfiles/colors/
Place GVimPortable.ini
at $HOME/../../
, i.e. the directory containing the GVimPortable executable