To be a good pentester you have to understand the basics of infrastructures: networking, various operating systems, and even programming.
What is a blue team, and how understanding their methodologies is crucial to being a more effective pentester?
The importance of certifications, and which cybersecurity certifications are worth it for pentesters, and which ones aren't?
My recommendations for the best hands-on experience you can get online, for everyone from absolute beginners to advanced hackers.
Every hacker has their own methodology, but cybersecurity organizations have compiled testing/attack frameworks that you can model your methodology off of.