For most Sample Lab I’d recommend at least a quad core CPU, 16 GB RAM and a fast SSD with at least 10 GB per VM free (although for Nano Server VMs only 800MB is required).
The amount of disk used is minimized by using Most Labs use DSC to configure each VM once it has been provisioned, so the ability to download any required DSC Resources from the Power Shell Gallery is required.
Note: The individual virtual machines are configured using Power Shell DSC after they are first started up.
This means that it might actually take some time for things like domain joins and other post configuration tasks to complete.
I have been struggling to fix this rather weird disk space issue for quite some time now.