You could try Comodo Adblocker for IOS & Android. CAB uses local VPN & can block ads on apps, websites, etc...
Give it a try & see how it works for you.
And I guess CAB doesn't work with any VPN software working on the system. You will have to disable either & use only 1.
If it is possible, use these apps in offline mode.
In my country, by clicking on certain ADS, especially if they are contained in unofficial apps, there is a chance to stumble in the activation of payment services (premium sms, etc).
Yes, advertisement pose security risks, cause those developers who organize the software with bundled ads are not controllable on what will happen; they just focus on revenue instead. But if you are a vigilant user then even accidentally struck on a website hence you will not accept to install any programs as first sign of trap.