IPPSEC’s videos on youtube are amazing. Other than that you could read others’ writeups. The problem (and also the beauty) in “hacking” is that you always need something else 
(okay not literally always but very often) Therefore the broader and deeper your knowledge becomes the better you’ll get.
IMO some absolutely necessary knowledge (or more like knowledge that’s always required) is basic networking, deep unix, some windows/powershell, decent and fluent, deep knowledge in at least a few programming languages, and a sh#*!tload of ‘searching’/googling affinity/knowledge. Python is very much recommended too as it can make your life that much easier many times.
If you have these and you take up some of the methodology / basic skeleton-structure of what IPPSEC is doing I think you’re looking at a great start