I'd like to offer some skill sets that have marketable skills:
Probability & Statistics - especially calculus-based probability and regression modeling or econometrics. Statistical programming in R or SAS goes hand-in-hand.
Object-Oriented programming & analysis
Database design & implementation
Data mining, data warehousing, machine learning.
If you want a detailed explanation of Data Science then do check out Intellipaat’s blog which will help you in understanding DS.
You can get a hands-on project by referring to the following Data Science Online Courses by Intellipaat which will teach you Data Science from scratch to advance.
And if you are more into videos then do check out the following video tutorial which will help you in mastering in the field of Data Science: