How about we limit the ranked matches to 3 per month, excluding any tournaments that may be ongoing?
To work off what Melon said, if the base points per a victory are 100 points. You can only challenge someone a maximum of 300 points more than you. i.e. Player A is 1000 vs. Player B is 1300 points. If player B wins they get the base 100 points (now 1400) and are now no longer within Player A’s range for fighting. If Player A wins they get the base 100 points + 10 points per difference or +30, giving them a victory total of 130 points. Player B, being the higher pointed player, loses the 30 points and drops to 1270. Player A then rises to 1130.