I read and heard from many that facebook is not as once it was, I do not know how true is this , for many reasons which account banning is one.
Lets say I've solved the problem of having accounts to advertise, is FB still a viable option now? can it bring more revenue than , or equal to, POP or mobile marketing? And is it suitable for a beginner? What type of offers should I run?
Any help is greatly appreciated.
Hey!
Despite the increasing complexity of running ads now, Facebook remains the largest social media platform with lots of diverse traffic and really interesting targeting options. Since all the banns are coming from simple wish to create great user experience, the solution is to advertise something that does not bother the users. Facebook is strict over spamming, adult content, misleading ads and rotators (such as Smartlinks).
Therefore some of the offer types that go well on Facebook are native and e-commerce (some apps, games could work well too). Make sure you really know the trends and interests of your target audience, explore before running a campaign.
Best of luck! 
Facebook is huge buddy. The volumes are incredible.
However, its not easy and maybe not the best source for beginners (but thats not to say you shouldnt look to use it as a source).
Brand offers, eCommerce, Travel, games...
Those are verticals that are suitable.
It can be great of course for Health, Biz Opps, Dating (and pretty much everything) but that would require some "handling" as they are not ok as far as FB terms say.
The beauty of FB is the amazing targeting you can do...
What type of offer was it?
Is the brand well known in the GEO(s) you were promoting?
What was the funnel?