There are lots of good online resources, even more than were available just a couple years ago. But "security" is a wide topic and nobody is a master of all of it. Here are my suggestions:
>Pentesting
Vulnhub and/or hackthebox.eu + youtube videos (e.g. Ippsec)
>Reverse engineering/exploit dev/malware analysis
Search on Amazon for RE and buy ~3 of the higher rated books. There are a few on that big book matrix that gets posted here that are good. Start doing crackmes and CTFs like Microcorruption
>Policy
Buy 1-2 Sec+ textbooks, study for 1-2 hours a day for a month or two, take the test
TLDR: Youtube, Google, various related websites, CTFs, books. If you can be more specific than "security" I can point you towards some good websites probably.