kalvincj
To use any of the Orchis-Grey gtk themes: Download Orchis-Grey.tar.xz from www.gnome-look.org. The exact link is https://www.gnome-look.org/p/1357889.
Extract the contents of the file. Open the folder into which the file contents have been extracted. The folder will be called Orchis-Grey. Copy the six folders inside the Orchis-Grey folder to /usr/share/themes/. Then open Budgie Desktop Settings and select any of the Orchis-Grey themes from the "Widgets" menu.
To use the Tela-Grey icon themes: Download Tela-grey.tar.xz from www.gnome-look.org. The exact link is https://www.gnome-look.org/p/1279924.
Extract the contents of the file. Open the folder into which the file contents have been extracted. The folder will be called Tela-Grey. Copy the three folders inside the Tela-Grey folder to /usr/share/icons/. Then open Budgie Desktop Settings and select any of the Tela-Grey icon themes from the "Icons" menu.