This app was mentioned in 4 comments, with an average of 1.00 upvote
Summoners War? Fits all your criteria. Game is F2P, and you can do pretty much everything without spending a cent. I've been playing for about 2.5 years now, I've tried similar games and nothing compares. High level PVPers tend to spend a lot, but if you're lucky enough with the monsters you summon you'll be able to compete.
The subreddit is full of shitposts, but there is a lot of good info in there too. /r/summonerswar
Linkme: Summoners War
edit: Light: Fellowship of Loux is another good game by the same developer. I would play it more but it runs like shit on all my (fairly old) devices. Maybe you'll have a better experience.
Light, produced by com2us but developper by a little studio. Quite new, I bet you can get to top 20 - 30% without spending a dime.