Programming. This is an essential skill. It can be atleast two languages from Java, C++, Python.
SQL – must be proficient in using SQL. Also look into variants such as NoSQL
Cloud Computing – Cloud is where the data is so it is essential to learn about technologies related to cloud computing, especially Amazon and Google cloud products
Mobile computing basics – Most applications are shifting to the mobile platform and hence one must be familiar with mobile app development, protocols, HTML5.