For rpg, have you played A Bard's Tale? If not, have a look...if so, what did you think of it?
Already suggested this in another comment but my favorite to play in quick spurts is 10000000. It's a really odd mix of genres (dungeon crawling via matching swords/spells/shields/materials), but there's just something about it that works for me.
I'm trying to use a $5 credit I already had from April in addition to my coins. I just purchased Out There, and now I'm considering Fiz (I love sim/tycoon type games but have zero interest in beer) and Monument Valley to use up some more credit.
I don't buy many apps, but I can recommend:
Plague Inc (try to eradicate all life on earth)
Pathogen (really chill strategy/puzzle game - just take over more of the board than your opponent)
Rebuild (post-apocalyptic turn based strategy - recruit survivors, assign jobs, find food, reclaim buildings)
10000000 (dungeon crawler/match game)
I know you already have 10000000 but seconding your rec for others looking for suggestions.
Edit: added Rebuild, forgot about this game but it was enjoyable enough that I did a rare 2nd playthrough.