Use your weapons equally

The fundamental rule of Dynasty Warriors: Origins’ leveling system is that your weapon types—not your protagonist—gains experience. The more you level up all your available weapon types, the more stat increases and skill boards you’ll unlock.
Weapons can still earn a modicum of passive experience if you don’t use them. However, to best maximize your power, you should use your weapons as evenly as you can. You’ll inevitably feel more comfortable with some weapon types over others, so I recommend saving your best weapons for major story battles while you use the armaments you’re least confident with during side missions or less eventful stages. Weapons require exponentially more experience points to level up as they grow in rank, so don’t let your growth plateau just because you only want to use swords.