How to promote my directory ?

Hi everyone,

I have a directory with approx. 1500 websites registered in. I am making 4-5$ with adsense/day.

I would like to know what is the best method to promote my directory ? i have about 10-15 registrations/day but i want more.

What is the best BH solutions ?

- Backlinks with scrapebox, I already made more than 100.000
- Tweetattacks ?
- Other ?

Thanks for your help!