Level 1 - Intro
Introductory CTFs to get your feet wet
Level 2 - Tooling
More introductory CTFs
Level 3 - Crypto & Hashes with CTF practice
Level 4 - Web
Level 5 - Reverse Engineering
Level 6 - Networking
Level 7 - PrivEsc
Level 8 - CTF practice
Level 9 - Windows