Hi,

I would create a list of influencers to build a list for this niche, this will also help you build you list.

I would also advertise on facebook, Instagram etc.

What exactly are you doing?

The simple way to build good quality buyers list is finding a company which specialize in lead generation. On the Internet, you can find a lot of these type of companies. They will help you for each step of the process.
Let me know what exactly are you doing ? After that, I can help you better.

For fashion and beauty niche, I would start with social media platforms such as Instagram and Facebook. You could also try following the beauty bloggers, see who follows them, and try to get into a partnership with the fashion and beauty influencers. But that's just me.