Twitter advertising may be just the right mix for your job board. I have started to experiment with them and find them to be effective at driving clicks to my site. And its cost effective too as you can see from the image below. They sent me a nice summary of what I spent and how many engagements my ads got. Just go to ads.twitter.com to get started.
Job Board Ebooks: https://gumroad.com/jobboardsecrets