How do you turn sports betting into something like investing?
I don't think if that is possible. Gambling can not be treated as investment since it's a game of luck, you wouldn't know the outcome of such investment, The chances of getting your profit back is low. You might even not get something in return in a long run.
What mindset or approach do you use to treat it seriously, like you're managing a portfolio?
I believe this question belongs to those that claim they use betting as investment.