Ask HN: Where do you advertise online?

Just started a business www.pleasereturn.me which sells recovery labels for devices. Going well so far, we have roughly a 75% return rate but we want to grow our user base (Who doesn't?).

I am curious to where you advertise online, if there are any niche services that have worked out well for you, or if you can recommend something for our service.

Another nagging question I've had, how is advertising on Facebook compared to Google? Better or worse?

Thanks HN