One of the quickest and easiest ways to change the look of your device is to change the font. It is pretty easy to do this if you are rooted. You can download the font you like, change the name, and place it in the appropriate folder with a root browser. This will change the font system wide, but if you wanted to change the fonts on a per app basis it would be a bit more complicated. There is now a quick and easy tool that allows you to change your font both system wide and also on a per app basis. Fonter by developer "Goodevh" will allow you to choose from many fonts. This is available in App form or Xposed Framework module. The app version doesn't require root privileges on Samsung and Oppo devices, but other devices like HTC, and Motorola will require root. The app also has built in themes. Head to the link below for the download.
via XDA