Andor’s Trail, it’s barely recogniseable as a “phone” game, other than that it does indeed run on phones. I don’t remember if it had ads or anything, been taking it from phone to phone for over 10 years now. I don’t think it had ads or anything. It’s open source, but has a pretty consistent feel despite having like 50+ contributors so far.
It’s an adventure RPG. The low level experience might be best with a bit of grinding, but… casual grinding… lol. I kind of just wander around collecting “meat” until I feel strong enough to leave the areas near town and set out on the rest of the adventure. But there has been alot more work around town since the last time I started a new character. So it might feel more natural now.