Change ionic default font


I know this question is asked and answered before in the links below. I want to change the default font without having to add to every css.
Things I have tried:

  1. Changing the .tff, .eot, .woff, .svg file directly to merge my fonts and ionicons
  2. Tried to implement the font by specifying it in html and css file (it works, but i want it to be default)
  3. Overwrite the www/lib/ionic/fonts with open-sans font (the ionicons disappear)
  4. When i use the first link (all formatting is gone, only left with text and buttons) I also tried placing the font-face on top and bottom in scss/

Please help! The answers i have seen are instructions but no explanation how it works. I don’t know how “ionic setup sass” works/what it does. How gulp plays a part in this.