I'm completely new to the concept of hosting a server with mods.

I'm trying to install the gather mod but have no clue how to do after adding the plugin to 'RustDedicated_data/plugins'

Not sure where to go from there I'm hosting a rust server with Shockbyte and managing files with Filezilla.

Thanks.

That is not where plugins are installed. See https://umod.org/documentation/plugins/installation