Hey!

after your bachelors in computer science engineering, you should be doing masters in cyber security systems to be a "post grad hacker". but in reality, to be a hacker you dont even need a school pass or under grad pass. all you need is the skill and the motive. so to become ethical hacker,  there are various course offered in institutions which are no degree but only certificate courses. so apply for them. do internships in cyber security companies. learn stuffs. thats how a real hacker is made.

learn java, c, c++, python for basics, then apply for some certificate course related to hacking. that alone can help you.

good luck