Penetration Testing–also known as Ethical Hacking–takes time, patience and perseverance to truly master. Paid training is probably worthwhile, however you will only get out as much as you put in. Practice outside the classroom is essential! Below is a list of some useful resources to help you get some of that practice.
Please note! I have not personally explored all of these links or taken each course, I would love to get feedback both positive and negative so I can keep providing high quality resources.