What (Linux based) OS do you recommend?

With Kali when comes to upgrade it has tons of upgrades from strange locations - what do you need the system for? It's best to have a user-friendly system like Debian/Ubuntu/Arch and run virtual machines from it - install one for Kali and 2-3 for next.

Also try to find Nessus cracked somewhere.

Ubuntu is a good system
It is the most friendly for beginners.

I would recommend either Kali Linux or Black Arch linux, both provide a ton of tools and are constantly being updated