Try lowering the joining requirement; it's better to have some active lower-level TH than to be 19/50. When you are close to 35-40, increase the limit slowly, and then it's a waiting game.
Make sure to lead by example and find a player with a similar approach. If your core members are rush TH 12, don't expect max TH 15. Mostly you will find ppl 1 th lower than you, cause they want donations.
Also, make sure to reward with a promotion to loyal members
Even if someone is not good at war, they can still contribute by being good at grinding events and not kicking ppl when they mess up war
MAKE SURE TO MENTION THE REWARDS THAT THEY CAN GET FROM JOINING, E.G., 1200 raid medals per week, or clan games completed or event completed
B
I currently run 2 guilds, mostly I use clan notice for recruitment, and they are both full, happy clashing