if you're reading this before starting the game then you're doing yourself a good thing ;+)
Supposedly this is the last achievement to get it, basically while you're going for 5-starring each song, if you couldn't 5 star a song first try, don't choose restart the song, go to song selection and choose it again. this way you'll increase the number of the stars you have in your account.
There are six characters, three males and three females character.
for the male character you'll need 37 stars to buy everything for it (20 stars for headwear, 12 for glasses & 5 for the outfit) whereas the female character will require 32 stars for everything (15 for the headwear, 12 for glasses & 5 for the outfit).
In total: (3 X 37) + (3 X 32) = 111 + 96 = 207 stars you'll need to buy everything.
Chances are you'll need to play few more times after you 5 star every song in the game, as in my condition I had to play about 8 more songs to get to the required amount of stars.
hope this helps :+)