Root it using fastboot or Odin, Fastboot (fastboot flash update root_yourdevice.zip) wherever your device is build and model, and if you downloaded it, and flashed it, you'll get free root access, You download the adblocker from jrummy apps, and install it, then switch on ad block to ensure that no ads are coming out of the Facebook or browser app, If on browser, still getting ads, you download AdBlock Plus for browsers android to ensure that no ads are coming out of the browser.
Please note that the rooting process takes 2 reboots.
Why reboots?
Reboots are the important part of flashing, fastbooting or going to recovery to ensure that the changes are exist and complete.
Reboot 1 does: Your device waits for your computer to enter fastboot commands, and then says that is flashing via OTA.
Reboot 2 does: Your device adds android guy icon and his friend the spinning blue wheel and the device is configuring for the root process, says reinstalling Android, but it is rooting.