iMovie is my favourite video editor to I recommend to beginners. It’s a shame that the software is exclusive to macOS and hence neither Windows nor Linux user can enjoy this editor. However, If you do own a Mac, you must know that iMovie comes pre-installed with your Mac which essentially makes it free. But that’s not what makes it best for beginners. The best part about iMovie is its simple and intuitive interface which is really easy to figure out, even without help. Also, Apple’s optimisation makes iMovie a really snappy editor which can be used even on older Macs without any problem. As a beginner, iMovie is the best video editor you can use on a Mac. I say this especially because iMovie acts as a really good primer for Final Cut Pro, which you are essentially going to use as you get more and more comfortable with video editing and iMovie no longer satisfies your requirements.
You might find that the free video editing software above are either too simple to meet your demends like audio editing and color correction, or too difficult to understand the workflow, then you should look at Wondershare Filmora9, which has significant improvement in overall performance, making the product faster, more powerful, and taking the user editing experience to a new level.