first of all you dont win extra ToriCredits because you are a higher belt.(as far as i know)
and you only win 10tc in official servers.
you can win more tc per game by purchasing a
booster
these last for a limited period of time
you can also win extra tc by winning one of the 500tc tournament servers.
Alternatively there are server types which allow increased amounts of tc per win by placing a entry fee for the match.
these are called duel servers. the server will take away the amount of tc set as the duel (e.g. 1k) and give double that back to you if you win, not returning it to you if you lose.
Betting work similarily however you dont need to participate in the fight, you can just type /bet [username you think will win] [tc] (excluding the "[""]" ofc) and the combined pot of everyone who bet will be split between the betters (who won there bets) at the end of the match
Hope i have been of some help