what do i do after i defeated n in pokemon black?

Answer 1

There are still a ton of things you can do after defeating N. You can enter in contests, fight in the Battle Tower, EV train your Pokemon to fight online, or just complete the rest of your Pokedex. The game never stops!

Answer 2

You also now have access eastern parts of Unova from route 11, east of opelucid city, which well lead all the way around to Nimbasa City.

Answer 3

If you're looking to train go to the route up from Black city or White forest and ride in the middle up and down the stairs in the shaking patches of grass theres about a 80% chance you'll run into an audino give your first Pokemon the lucky egg to boost exp i got 9k exp from a lvl 50 one. Note: turning on a repel before entering grass keeps you from having an interference through reaching your patch of grass.