My thoughts are you should stop paying by the month.
I just wanted to give it a try, so one month seemed to be a fair shoot.
I already tried many engines, and Construct 3 seems to be quite good, but I am worried about how the engine handles full games, I don't want to finish something and notice compatibility bugs. Specially regarding the Admobs.
I've heard that these plugins of Ads are somehow outdated, and Android export isn't accurate, but those are things that I don't really understand, so I wanted the advices from experienced developers about the subject.