Before anyone chews me out, as this effectively renders many free apps equivalent to their premium (ad-free) counterparts, I usually pay for said premium versions to compensate their developers.
Using adaway or a pi-hole for that matter will not - they will only cause ad loading to fail (in some cases) - which sometimes results in frames showing errors on the page instead of a clean rendering of nothing with ad divs removed.
Personally I wind up using several methods - AdAway to kill most app ads, uBlock for web and Xposed to kill YouTube ads since the hosts-based methods seem to work rather poorly for them as their subdomains change all the time.
That's weird, I didn't get any Youtube ads in quite a long time, and only use AdAway.
Defense in depth.