How much can I make per day online if I'm good with programming?

This is kind of a crazy question with a lot of room for interpretation.

If you were really good (and are based in the USA or are a US citizen), and are able to pass coding challenges on places like HackerRank, LeetCode and other places, you could feasibly get a job at a company like Google / Facebook. Those programmers start at like $250K / year, not counting stock options and the like.

I've heard some people say that the best machine learning programmers might cost a company $1M / year.

There's no better path to riches (meaning working for another company) than getting really, really good at programming and being able to pass programming interviews.

All you have to do is focus on what you excel.

You’re going to have a tough time finding good jobs on freelancing websites without a good portfolio/repo.