Enter the Skill Shop while holding down the L2 button. Bulma will talk, but just leave, while holding the L2 button still. Re-enter the shop, repeat the trick over and over and your percent of your Capsules keeps increasing. This also unlocks characters for you, Breakthrough capsules, fusions, everything.

Collect the dragonballs and earn the breakthroughs for Goku, Hercule/Sataan, Yamcha, Tien, and The Supreme Kai/Kaio Shin. After that, gather the dragonballs again and earn their fusion capsules.

Nappa: Beat him with Vegeta in Dragon World
Raditz: Beat him with Goku in Dragon World
Recoome: Beat him with Goku in Dragon World
Captain Ginyu: Beat him with Vegeta in Dragon World
Frieza: Beat him with Goku in Dragon World
Android 20:Beat him with Goku in Dragon World
Android 18: Beat her with Krillin in Dragon World
Android 17: Beat him with Piccolo in Dragon World
Android 16: Beat him with Goku in Dragon World
Cell: Beat him with Goku in Dragon World
Great Saiyaman: Beat Cell with Gohan in Dragon World
Hercule: Beat Majin Buu (fat) with Great Saiyaman
Videl: Beat Super Buu (with Gohan absorbed) with Hercule
Future Trunks: Beat Vegeta on Namek with Kid Trunks
All the Buus: Get all of the dragonballs in dragon world and wish for Babidi's spaceship. Then do any of the stages in Babidi's ship to gain kili. If you have enough kili you can unlock the Buus automatically (a capsule would show up when the kili is being collected at the end of each stage).