I used to read a lot about sports betting also worked in this industry and i am currently investing in it. Basically the whole concept behind it is to find an edge against bookmakers and by that i mean you should find opportunities where bookies picked their odds wrong (they underestimate certain outcome and give higher odds than real odds) only in this case you'll win longterm.
For example, imagine a coin flip, if we make a deal for you to give me 1$ everytime when it's Heads and I give you 0,9$ everytime when it's Tails. In this case scenario i'll be on profit, because the chance of flipping Tails or Heads is 50% for sure if we flip the coin for long enough.
So the idea behind it, is to be very good at certain sport so you can research, find better info, analyse matches better than bookmakers so you can find value in certain pick you make.
The real value picks are hidden behind not that popular sports, because bookies do not have that much of info and specialists - horse betting, golf, hounds etc, low football leagues (even though i wouldn't recommend football at all or maybe live picks only if you have the time to spend it).