If you like deckbuilding games like Ascension then you really should get Star Realms. It's free to play offline and $3 IAP unlocks online MP and campaign missions on all devices with one login.
There's some mini expansions for $2/ea and a major expansion for $5 but you don't need any of that until you feel like you want to shake up the gameplay with new mechanics.
It's one of the best card games on mobile and you can get it IRL for $15 with enough cards for a 2 player game.
They have a new digital deckbuilder adaptation of their game Epic coming soon, really excited.
Age of Rivals is also an awesome and unique deckbuilding game but it doesn't have pass n play so i left it off the list.
