I think the answer is very simple, big rewards
that's all.
When you bump your faucets prize ratio, people will do all the promotion for you.
Referral commission + good rewards and you wont be able to catchup on growing traffic.
Promo time have to be like a month or so for good and strong user base.
Anti bot systems is a must. I see that your doge faucet for example, pays 1,2...5 doge per claim, doge is cheap now, make an experiment with this site, triple the rewards and observe the magic
Really its all you can and should do, dont bother with boring ad campaigns or traffic boosters.
Give big and they will come.