On S1-Mod, the search paths for custom game scripts are as follows:
ALL MODES:
scripts
SP:
scripts/sp
scripts/sp/<level name>
MP:
scripts/mp
scripts/mp/<level name>
scripts/mp/<game type>
Unlike IW4x, IW4x-SP, and IW5-Mod, the S1-Mod (and IW6-Mod) do not have a userraw folder.
Take S1-Mod as an example:
The base folder for GSC scripts is simply the s1 folder. This folder likely already exists in your game directory. If it doesn’t, you can create it manually like this:
Call of Duty Advanced Warfare/s1/scripts/mp/example.gsc