BSD is also an option...

OpenBSD is great for a very lightweight OS for older computers

nullama

i think it really depends on how deep you wanna go into Linux as a whole, but I found it helpful to learn a few terminal commands when i first started on an ubuntu-based distro. commands like "sudo apt-get update" are pretty basic and are a good starting point. 

Here's a [link](https://ubuntu.com/tutorials/command-line-for-beginners#1-overview) that can help get you started

I just started using Ubuntu a couple of days ago... What will the most important thing to learn for a newby? Any video tutorial that you considered a must watch?

Thanks! 