When you pass mission 16, you can get as many red orbs as desired. Go up and down the elevator, killing all enemies. Remember to mix up your attacks to increase your stylish bonus. Do not use a maxed-out weapon, as this will kill enemies too quickly and not allow you to get your stylish up fast enough. If done correctly, you can get up to 2,500 Red Orbs on each trip up and down the elevator. This may get tedious, but is well worth it when you get to the "Must Die" modes. Save your data when you have the desired number of orbs.