Can anyone help me in suggesting the best course preferably to learn as a fresher?
Would it be better to go with AI or Machine learning?
And certainly what will be the duration and methods of learning this course ?
Machine Learning is a type of AI. AI broadly includes symbolic rule-based approached we used many years ago. Today the paradigm is Machine Learning, i.e., we train systems by giving them examples of input and output signals, rather than program rules for every situation, which doesn't really work for complex problems.
TL;DR - Machine Learning is what you are looking to study, and that is the most prominent type of AI you should care about right now