what do you have to do to win the top of the tower

Something like this:
To even get there you must have completed every Street (at least Level 1), beaten every Club and every Executive. Then you have to beat Lady. Only then do you get to face Boldo-he's got every song, every movie clip, and every trick in the book. To even have a chance of winning you must pick a song you've acquired (they have a musical note in the upper-left corner on the music select screen) to start with, then hope you get those songs at random, as well as songs you have lots of movie clips for (On Air lights up above your character when it's a clip you have). If you get a song you don't have (dance gauge does not turn yellow/orange) then you can't gain any ground, even if you AAA it. The big thing is just stick with it-sometimes it will take 7-8 songs to build it up enough although I've beaten him several times with just 2 songs. Hint: More often than not, based on my experience, Still In My Heart (Momo Mix) is the song I win on. Oh yeah, it helps to do the songs on Expert or Oni. When you finally beat Boldo you get a final ranking based on your progress so far and you also get the final song-Insaner L.E.D.'s Punishment Mix.

If you're stil having trouble, go back to replay Streets to collect more songs and movie clips-they'll be offered for purchase after a stage if you have at least 500 dollars (cost of each). Get as many as you can otherwise you have little to no chance of winning.

Or just take it like a man and use PARANOiA Survivor Max on Oni. You have room for little error so don't screw up more than a second in there. If you're doing well, you should actually win around the beginning of the hell runs.

And remember, when you win, STOP. You only need to beat your opponent, not the song.