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 really enjoyed M&M: Clash of Heroes. It's my favorite puzzle/RPG hybrid. It's the only one that the combat system feels like actual combat rather than arbitrarily match 3 gems to unleash attacks and is a good mix of strategy and puzzle. The story is decent and the game is 25+ hours long. Though the controls on mobile may sometimes be clunky and make you waste turns.

And then there's Majesty. It's the PC game remade for mobiles. It's basically a base building RTS where you can't control your units. Rather, you hire heroes which can level up and set bounties on monster lairs to encourage them to go destroy those lairs. I've played approx. 10% of the game and liking it so far.

The Bard's Tale is a humorous hack & slash RPG that was ported from the PC/PS2. It's very cheap for what you get. I've played it a long time ago on the PC and it's fun.

Apart from those I'm probably in the same position as you. Got 3 games that I haven't played yet and have 1500 coins left, not sure what I should buy.

The games I bought are:

Prince of Persia: The Shadow and the Flame just becaused I liked the POP games on PC and it's kinda cheap.

Symphony of Eternity, probably a standard JRPG by Kemco.

Doom & Destiny, a humorous, nerdy RPG which I've seen some people at /r/androidgaming say that it's quite good.

If you like management games try games made by Kairosoft. I've never played any of them but a lot of people say that they're good. They have free lite versions you can try on Googleplay