Ascension is my most played by far. It's one of the earliest deckbuilders and the first one (I think) with the river-style market which has been used in many other deckbuilders since. The developers have done a great job exploring various mechanisms in the expansions over the years and most of the content is available in the digital version too. My favorite sets are the ones that use Insight (the amber gems): Dreamscape, Delirium, Deliverance.

Besides the game mechanics the great art, music and the smooth app make it very chill and enjoyable for me.