Successfully complete the game, and save when prompted. Load the cleared saved game file to start a new playthrough and gain access to the Grade shop, where you can purchase the following bonuses with Grade Points:

1/2 Level (2,000 Grade Points): Retain half your maximum level when starting a new game.
AC +2 (1500 Grade Points): Increase the maximum AC of your character by 2.
Accessories (700 Grade Points): Carry accessories when starting a new game.
Arts (2,000 Grade Points): Retain your Arts and Arts-related item when starting a new game.
Arts Count (100 Grade Points): Keep Arts Usage data.
Consumables Items (300 Grade Points): Carry your consumables items when starting a new game.
Critical x3 (100 Grade Points): Triples critical rate, including enemies.
Damage x2 (100 Grade Points): Doubles damage, including enemies.
Drop Rate x2 (500 Grade Points): Doubles chance of finding items after battle.
Experience x2 (300 Grade Points): Doubles experience earned in battle.
Experience x5 (2,000 Grade Points): Quintuples experience earned in battle.
Full Level (5,000 Grade Points): Retain maximum level when starting a new game.
Gald (1,000 Grade Points): Retain your Gald when starting a new game.
Gald x2 (300 Grade Points): Doubles Gald earned in battle.
Link Gauge (500 Grade Points): Doubles the rate of the Link Gauge.
Material (500 Grade Points): Carry your material items when starting a new game.
Material Point x2 (300 Grade Points): Doubles the rates of material points.
Max 30 Items (500 Grade Points): Increases item limit to 30.
Max 99 Items (1,000 Grade Points): Increases item limit to 99.
Max AC +1 (500 Grade Points): Increases the maximum AC of your character by 1.
Monster Data (500 Grade Points): Retain your monster logs.
Shop Level (1,000 Grade Points): Retain your shop level when starting a new game.
Skill SP 1 (3,000 Grade Points): All skills are reduced to 1 SP.
Special Item (200 Grade Points): Start new game with Winged Boots and Arts Ball.
Unlock All Skits (300 Grade Points): Unlock all skits under the "Library" option.
Visual Item (200 Grade Points): Retain your appearance item when starting a new game.