Human resources use a bit of both of those. Advertising and using social media to recruit qualified candidates is common practice. HR is also a career that offers plenty of advancement opportunities to move up in the company and take over different aspects of the HR functions based on your specialties. I would suggest taking some business courses as well if you choose this route.
Coupling Advertising with Business or PR
with business would work well too if you do not want to work in HR but rather on the more creative side of things.