I just happen to need to do a re-install of my Kali VM so it's just the right time for a step-by-step tutorial on how to Install Kali Linux on VirtualBox with Guest Additions!
I always run Kali on a VM. Even on my Hackbook. Why? Because you can always use a snapshot to revert the VM's state back to a freshly installed period when you mess something up badly - and trust me, it happens.