It is tempting to download and install every plugin, call-out pack, new vehicle, exciting siren, new and greatest feature. Slow down, mistakes will cause game crashes and ultimately lead to frustration which could lead to a disinterest in the game entirely.
From here on out, only install one modification at a time, in the event you did it wrong or something goes haywire, it will be easy to understand what the problem is.
Rule #3: Use a Mods Folder
Later you will want to install custom uniforms, vehicles, weapons...etc Never alter or edit your original vanilla game files, you instead utilize a mods folder with copies of the original game files for modification.