As a bettor, I'd avoid those type of leagues because they're prone to selling matches and your bet might not be justifiable if you lose it when you have the idea that it was once a sold game and your money doesn't even able to fight for it.
You can't do anything as the game can be manipulated by people who has a good control regarding to the game, something that we can't avoid to happen inside those small tier leagues, it's better if you can do your research and study those major leagues which can help you address every factors that you use when analyzing games, understanding and knowing both potential and edges by the team that you are following might help you plus knowing that big leagues is not prone that much with any possibility of fixed matches (not generalizing) as we can still hear rumors about some game fixing.