"REDTEAMer first step". (Link list)

[KAJIT]

http://gtfobins.github.io/

http://lolbas-project.github.io/#

http://ired.team/

http://adsecurity.org/

http://0xsp.com/

http://red.y1ng.org

http://book.hacktricks.xyz

http://bbs.pediy.com/

...and u if see it - u know about xss.pro XD. ( just see articles here )
......and read more admins\devops blogs - pentester -> its the alter-ego of devops