Dragon Ball Z: Buu's Fury Hints

Q: What level should I reach in order to defeat Kid Buu?
A: This depends on how skilled you are. Goku and Vegeta should be at moderately high levels. With Goku probably at level 160 by now, I suggest raising Vegeta up to at least that level before you start the final battle.

If you need more time to regain energy, all you have to do is hide behind the rock that Goku or Vegeta is standing on. Wait 10 seconds after you get back there, to make sure Buu isn't following you.

First beat the game. Then go to fukuru forest. Open the gate. Go forward until you you see a black ninja. Talk to him and he will give Exhibits for each bandanna you have.