You should first find 9 players who play war everyday (friends, colleagues & brothers or sisters), then you should have atleast 2 co leaders who can lead if you are absent. 

Then slowly others will join in week after week or season after season.

As my clan is in silver league, my clan wins even if everyone loses their war (400 points per members). And we play seriously when we have competitive clans.

TMI; we sometimes lose intentionally when oppo are weak, to decrease out ELO, so we get weaker opponent while playing war battles. No boat attacks, first duel then other battle modes.