I had a ton of fun with Clash Royale for many months (even years at this point) without spending exactly zero money. I think the way they mix free players with paying players is absolutely brilliant (from a perspective of free player).

If I go against a player two levels ahead of me, I can be pretty much sure that he bought his deck and since he's going against me not some higher rank I know I have chance of winning if I can outwit materially stronger opponent.

When I'm going against someone with lower level then I can be sure that this guy has very carefully crafted deck and is a very skilled player.