It's probably best to buy a single-piece power supply (a wall wart with a cable having a micro USB plug) rated for least 2000mA as the very minimum (more is even better) and trying to avoid anything with generic detachable USB cables. The generic USB cables are simply not designed for more than 500mA and it's easy to end up with a bad cable. The Raspberry Pi 3 power supply is most likely one of the best possible choices.
The PINE64 has a pretty high peak power consumption, and even the CPU alone can draw up to 1600mA from a 5V PSU under really heavy load. And don't forget about the GPU, which can work simultaneously and consume additional power. Also having two USB ports means that the PINE64 should be ready to supply 500mA + 500mA to the connected USB devices too. There isn't anything particularly bad about this. The Raspberry Pi 3 has exactly the same problem and needs a decent power supply too.
The PINE64 has a pretty high peak power consumption, and even the CPU alone can draw up to 1600mA from a 5V PSU under really heavy load. And don't forget about the GPU, which can work simultaneously and consume additional power. Also having two USB ports means that the PINE64 should be ready to supply 500mA + 500mA to the connected USB devices too. There isn't anything particularly bad about this. The Raspberry Pi 3 has exactly the same problem and needs a decent power supply too.