Data Science is the trending domain, which Harvard Business Review quoted as "The Sexiest Job of 21st century". You become proficient in something if you put up time and effort in it to study and master it. Data Science is the interconnection between the Programming field, Math, and Statistics. You need to master all three combined to be the master of Data Science.
You can rely on online materials that you find for free, but do you really think these resources will help you in becoming proficient in Data Science? If at all these materials made the difference, then there wouldn't have been so much shortage in the Data Science domain for qualified professionals.
I would recommend you take up Intellipaat's Data Science Master Course to help you master Data Science and become proficient in it. The course is designed by industry experts, offers you mentor support, at the end of the training you get to work on real projects, comes with Lifetime Free Upgrade, technical support, and many other benefits. This is an end-to-end course that means you can completely rely on these materials. I would suggest you take a look at the following YouTube video of one of our happy learners who were more than happy to share his learning experience with us.