Slowly. :) Four Lv.50 are in my PC. I have the fifth and sixth with me (the Pidgeot from yesterday with Fly and a Jynx that doesn't do well on Route 26, so it held the Exp. Share to get there). I know I have Scyther with me (replaced False Swipe prior to E4 and a nice array of different Type moves, will return False Swipe later via a TM) in addition to two Water types (due to the Ponyta on Route 26), and a Dugtrio (three Ground moves, will use if I find a weakness to it). Everyone at least Lv.45 or higher. Got a couple more in the PC close to Lv.50 that I want to get there including my starter (now Lv.49, gave it a rest to get others the focus for a while).
Once most of Box 1 is up to that level - excepting Lugia perhaps, but might battle with it too - I'll pick a team, head to the doorway to challenge, save my game, and see how it goes. If I find a weakness somewhere, I'll either change or level that weakness a little more to compensate then head back. I figure a couple of days, barring any trading and activity in Black, and I'll be ready to look into importing. :D I'm thinking of finding the types that are effective against Lance (like Jynx's Ice) and giving them Lv.51 or Lv.52.