Maybe
Guild of Dungeoneering? The best way I can describe it is it's a card-based roguelike game. I've had a ton of fun with it. It works fine on a phone (I use a Nexus 6P), and it's also a great tablet game.
Reigns is also a super fun game. I won't even begin to try to describe it.
And last but not least, I'll make a recommendation for
Templar Battleforce. It's currently out of your price range at $10, but it goes on sale occasionally. There is also a generous Lite version you can try out just to see if it's your type of game. The developers who make this game are hands down the best Android game devs around. They constantly update their games after release with free content upgrades, and their support is unparalleled. I highly recommend checking out some of their other games just to see if anything else interests you. They typically have free versions that allow you play a good chunk of the game as an extended demo. While Templar Battleforce is probably my favorite of the bunch, they do have a lot of gems in their catalog that I would suggest looking at.
Edit: I forgot about
Lost Frontier. That seems like it would be up your alley. It's a tactics game that is pretty fun to play. I bought it at launch and checking on it now I'm surprised it isn't reviewed better. While it's not as good of a tactics game as something like XCOM, I thought it was a great fit for a mobile device. These same devs made
Battleheart Legacy which is an interesting RPG in the same vein as Diablo.
