You don't need to buy anything unless you are trying to keep all pokemon alive. In that case you might want some max revives and hyper potions.
at the Pokemon league
buy Pokemon white
that isnt a real pokemon game.
nothing once you beat the Pokemon league it turns to a regular ship and takes you to the unity tower
They keep getting stronger each time you challenge them. at least that's what They do in Pokemon black.
at the Pokemon league
Beat the Pokemon league!
You can buy them in the Pokemon League Pokemon Center.
at the Pokemon league
First you have to complete all Gym Leaders & get all of the badges. Then you head to the Pokemon League.
If you havent beaten the Pokemon league then level them up a bit then defeat the Pokemon league
buy Pokemon white
in the pokemon league after beating the elite 4 talk to each 5 times them YOU HAVE TO BEAT THE CHAMPION WITHOUT LOOSING 1 POKEMON AND THEN GO TO THE BLACK CITY mart and you can buy master balls
Accelgor, Bouffalant, Escavalier, Druddigon, Vanilluxe and Volcarona and that applies for both Pokemon Black and White.
free roam
after you beat the Pokemon league
Buy it at the poKemon league