Where can I find 100% free audio/music for my projects?

I'm currently working on my portfolio for a 3D Environment Game Artist. I don't know much about audio editing or recording. I just know enough for the basic stuff of audio and music creation. Where can I find 100% free audio and music to use for personal projects and commercial projects? I want to use some ambiance sounds and music soundtrack for my showcase demo reel videos of my UE4 projects. I have tried to look around for free audio but I find it kind of difficult to find the right soundtrack or sound for the project, a lot of time the free audio just doesn't feel right or sound right for the project I'm working on. I am open to spending a tiny bit of money on music and audio which I could take a look at Unreal Marketplace audio store.