I am a programmer, how do I get into field of Data Science?
Focus less on gaining skills and more on gaining experience. Try to actually solve some problems and post your work on github. You'll learn more in the process and be able to demonstrate knowledge and experience to employers, which is much more valuable than having a supposedly deep understanding of a topic or theory. 

Data Science is a pretty loaded field these days so I'm not sure what kind of work you specifically want to do, but assuming that machine learning is a component of it then kaggle.com is a good place to start. In terms of goals, if you're able to work with the data in pandas/numpy/scipy, build models in sci-kit learn and make some pretty graphs in seaborn, ggplot or even matplotlib then you won't have a problem getting a job from a skills perspective -- especially if you have code samples and examples to demonstrate your abilities. If you get stuck then stackexchange will either have the answer or you can post a questions and you'll have an answer shortly. Once you're doing the work for a living then you'll learn even more, likely from a senior team member who mentors you.

Best of luck.