package management - Installing Offline Ubuntu 16.04 how to load apt-offline & install

I am installing Ubuntu 16.04. I'm looking for someone who knows that offline installer and update for driver's mainly system updates and wireless drivers, perfered legacy since my wireless card is an ASUS PCE-AC56 card.
When offline to use command sudo apt-offline I get 'apt-offline command not found' I've tried to install the package for apt-offline and the package is not found.
And finding that I need an apt Sig file generated, I can find what packages I need to download that my system will use to update... Another note, though the apt-offline psckage is not found when I try to install apt-offline. How do I generate the file then download it online to create an update package to update an offline system running Ubuntu. Thank you work arounds welcome and info on this is a great help.