I haven't taken the step yet to try out polymarket and from what I understand you can't invest in a token of the platform and there also aren't any fees?

When it comes down to prediction markets it kind of feels like the US Elections is the only real thing they are used for and unless they drastically change their interface I doubt many sports bettors will adopt it. Still very impressive volume numbers though! If you are looking for an exchange to place crypto bets, I would say test out sx.bet, their fees are turned off so if you offer bets you potentially can get great odds.