accessory not supported

I am getting a iPhone very very soon, but what do i do about my USB-C accessories? I play minecraft and some other games on my phone using the controller, but since it's connecting by USB-C I will cannot connect it to the iPhone, i don't wanna go through the hassle of getting another kishi, so...

my iPad Pro is showing weirdness. When I first wake it, it flashes the battery. While I’m reading a newspaper or pages on Safari, a “accessory not supported” dialogue box pops up. I press ok and go on. It’s an irritating interruption. Only happened after OS. 11updates.i reboot my devices...