At battle subway you go to the people at the desk and they ask you about gp?

Question

Battle sub

Answer 1

I'm pretty darn sure that you're asking about BP, not GP. BP is the currency of the Battle Subway, where you can exchange it for items offered by people on the counter for items, like Vitamins, Air Balloons, Eject Buttons, and even TMs. You can accumulate these points by completing 7-win streaks in the Battle Subway trains.