type of experience required for masters
My suggestion is that you continue your job as Master's programs in engineering departments in the US (at least for many schools) value the experience in the industry before taking on a Master's degree. As for personal projects, it is always useful to be able to present a few in your application materials; however, don't feel like you have to learn everything about computer vision, machine learning etc. before you apply for the schools. It is what the degree is for. 

Having done some amount of work is surely useful, as it shows your genuine interest in the field and being able to effectively articulate why you want to study a certain field in your application statement also carries some considerable weight when it comes to admissions. You can try to focus on a single, but a considerably impressive project on a related topic and present it in your application, rather than trying to take all the MOOCs out there (although Andrew Ng's courses are quite useful).