the answer is pretty simple... work backwards. Look at the exams and what material they cover. You can pick one course/set of videos to start with and see what they do and do not cover. From there, look at other courses that do cover and go from there. Study notes that have been posted online from people are also extremely helpful

Obviously depending on which exam you're taking (which you didn't specify), this might not apply. I finished the AWS CCP in 2 weeks and I started with the free course aws.training offers, took some practice tests from udemy, discovered that the free course didn't cover everything, found someone's notes and completed the rest.

There isn't one place that has all the answers. It's like asking to test you about physics, but the subject about physics is so wide and broad that there's no way you can find something that guarantees to cover everything. The key takeaway is to know HOW to study, not WHAT to study.