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.
If you like match-3 semi-RPGs, you might want to give Doctor Who Legacy a look. It's a free game (no ads, can even play offline) that plays like Puzzle and Dragons I think, but I'm mentioning it because I spent $4.99 to unlock the Fan Area in-game with unique stages and character unlocks. I liked the game enough to start over with the Amazon version so I could use my free dosh on it, so there's that.
Final Fantasy VI was half-price a while back, so I grabbed that. It unfortunately doesn't want to run well on my old tablet (Acer Iconia A500), but it's more or less a prettier version of the GBA game.
Chu Chu Rocket! is a unique puzzle game where you have a set number of tiles and you have to guide the cute mice to the rockets without any of them dying to the cats, holes, or having a cat wander into a rocket.
Let's see, what else have I bought...is there a place where Amazon tells you what you've bought, not just what you got from the Free App of the Day thing?
I kinda liked Star Command. Some people compare it to FTL, but from the little I've played, it seems it deal more with the inside of your ship than anything, and you can set up different rooms to strengthen your crew in different ways.
I would've liked Sonic 2 and Sonic CD if I was used to a virtual Dpad and buttons on a 10" tablet. It's somewhat difficult that way, but I read that I could use an Xbox 360 controller given I have a full-sized USB port, so I should try that... Both games are remakes in a new engine, but you wouldn't tell it normally.
Not a game, but Gentle Alarm did everything I wanted out of an alarm app. The free version works fine...except it won't do anything on Wednesday. >_> Speaking of non-game apps, I was going to suggest Sketchbook Pro, but it seems it's not on the Amazon Appstore anymore. I might spend $3.99 to get the in-app upgrade of Autodesk Sketchbook since I like drawing and have used the old Pro for a long time now. And I really have nothing else I want right now, so...
Bejeweled 2 is one of those no-brainer gets, though $3 might be too high for some.
I've heard Plague Inc. is good, and it's only 99 cents. Considering it's ~$15 on Steam, this might be a good alternative if you have a capable Android device.
I'm kinda grasping for hits at this point, but for all the games I've bought or gotten free, I've barely played any of them. Whoops.
My mom has around $25 waiting to expire. Any recommendations for someone who honestly casually plays slot machine games? She used to have interest in Bejeweled but that was on her laptop which she never uses anymore.
And a minor PSA for those looking to spend their coins: Mind the fact that you may be charged a tax in coins! Pretty easy to forget but I thought I'd bring that up.