Hello Alexandru,
You have probably found these resources already, but I wanted to post them here for future users.
Intro video to this method: https://www.youtube.com/watch?v=HAULM1WQkew
Gneiss / balance tree tutorial: Differential abundance analysis with gneiss — QIIME 2 2018.2.0 documentation
And finally, the paper itself: http://msystems.asm.org/content/2/1/e00162-16
Colin