What are the basics of CS i should know,before I start my journey into machine learning
Computer science is a very broad subject area, and many of its sub-disciplines have little or no overlap with others. For example, knowing the basics of operating systems design, compiler design or microprocessor design are unlikely to help you make progress in machine learning (although each one is an interesting topic in its own right).

Machine learning is a sub-topic of artificial intelligence, so the most closely related disciplines are other sub-topics of artificial intelligence such as pattern recognition, data mining, knowledge representation and natural language processing. Some knowledge of the theory of data structures and algorithms would also be useful. Outside of computer science itself, you will also need some knowledge of mathematical topics such as probability, statistics and mathematical optimisation.