Content Marketing: How often do I need to blog to keep my content ranking high?

It depends on your niche, if it's related to entertainment then you need to blog frequently like every two days. If it's related to fashion then once a week. Most of the industries are posting 4 blogs in a month. So I think that works well.

https://www.seo-ar.net/%D8%A3%D9%87%D9%85-10-%D8%AE%D8%B7%D9%88%D8%A7%D8%AA-%D9%84%D8%B6%D9%85%D8%A7%D9%86-%D8%A3%D8%B1%D8%B4%D9%81%D8%A9-%D9%85%D9%88%D9%82%D8%B9%D9%83-%D9%81%D9%8A-%D8%AC%D9%88%D8%AC%D9%84/https://ads.google.com/intl/ar_eg/start/?subid=eg-ar-ha-g-aw-c-0-s5_xx_txx_xx_xx_bau_non!o2~1486625736-285656456373-kwd-322835696305&utm_campaign=eg-ar-ha-g-aw-c-0-s5_xx_txx_xx_xx_bau_non!o2~1486625736-285656456373-kwd-322835696305

It all depends what you are bloging about but twice a week is okay.You should set up Social platforms so that you could promote your blog always. Social media will help in a big way.