There is a bug or a feature that will significantly boost your chances to progress in league at the cost of some medals. What do you have to do? You don't claim next weeks league reward for few days (I don't recommend that you wait more than 5 days) and in the meantime you loose as many medals as possible. Basicly you don't attack anyone until you get pushed into a league by claiming a reward. League opponents will be based on amount of your medals ATM when reward is claimed.
Example:
If I won previous league (or lost, doesn't matter ) with 1000 medals and I claimed reward on monday, I would have little or nothing to attack and my opponents have between 995 and 1005 medals.
If I waited for reward until friday (without attacking anything for medals), I would have about 960 medals and a lot of options to attack. Opponents would have around 955-965 medals and probably an empty map. It may be possible to advance with less medals than you had in previous league.
Example:
If I won previous league (or lost, doesn't matter ) with 1000 medals and I claimed reward on monday, I would have little or nothing to attack and my opponents have between 995 and 1005 medals.
If I waited for reward until friday (without attacking anything for medals), I would have about 960 medals and a lot of options to attack. Opponents would have around 955-965 medals and probably an empty map. It may be possible to advance with less medals than you had in previous league.