The one thing I'm not so sure of is if the Amazon fires OS is compatible, I think it's a bit custom to Amazon unless you root it. I posted a similar question awhile ago and was planning to buy something until Intel chips ended up being supported anyway. A nicer user linked me: Blu R1 HD Which is $50 for prime members or will give you $50 back when you sign up for prime. This would run the game fine but I realize it isn't exactly a tablet. As long as you make sure to meet the minimum requirements of the game in phone specs you should be fine, it's a mobile game after all. Also note that the Amazon app store doesn't have pokemon tcg online on it, you'll need Google play store or Apple store unless you use an apk.

Edit: Fire works confirmed by this user below.

Amazon already saved me. Let me get a $60 phone to play on

https://www.amazon.com/BLU-R1-HD-Exclusive-Lockscreen/dp/B01F9N5QXI

Edit: Seems to run

the phone has ads instead of your lock screen, but for 50$ it's no that bad

I don't think this will run it. It requires 2GB RAM, and this only has 1GB. Slow processor too, 1.2GHz 400 Quad core - doesn't cut it these days.

Do you have Amazon Prime? You can score a BLU R1 that will run it decently for $60

https://www.amazon.com/BLU-R1-HD-Exclusive-Lockscreen/dp/B01F9N5QXI