Neil Patel is a good first place to start to learn. Then you realize all his (vanity) metrics are just measures of your competition. So I went to Warriorforum.com to read what my competition was saying.

After that, I realized it was all about the basics + a niche. you need to know the fundamentals of "buy traffic, convert traffic to business goal, collect money for successful business outcome", but that was table stakes.

Once you know the mechanics of the game, it's up to you to niche/exploit. You're not going to make money doing what everyone else does, so if you're asking for advice instead of trying your own thing, you're already losing.

Find a product that you like owning but have difficulty buying. Identify and fix those pain points.