First Step of Dao Mastery

Daos are a fundamental understanding of the forces of the universe. By mastering a Dao, you boost your effectiveness in battle, with magic or a specific damage type, increasing your strength or defense, or make checks more likely to succeed. Mastering Daos is extremely difficult, and most only find enlightenment the heat of battle, or from unique experiences. I.e. at the DM's discretion, like milestone leveling.

Your understanding of the forces effects how your Dao evolves. In game, imagine what your player uses the most of their Dao and boost it, or add extra damage/effects to their attacks. Make them magical, bypassing resistances, or extra abilities.

Work with your DM to choose the type of Dao you want to master, starting with a early stage Dao seed of your chosen type. You could, for example, choose the Dao of Blades. When using bladed weapons you get a bonus to hit and to damage. This could give you a +1 to hit and +2 to damage at the early stage, and +4 to hit and +5 to damage at the peak stage. 

It evolves along this path:

Dao seed: Early-Mid-Late-Peak

Dao Fragment: Early-Mid-Late-Peak

Going from a Dao seed to a Fragment should be a large boost in power. This can grant additional spells, effects, or abilities at the DM's discretion. In the example of a Dao of Blades, you can grant your PC the effects of the Great Weapon Master feat to their Dao effects for evolving their seed into a Fragment. 

If any of you have read the Defiance of the Fall series by JF Brink, you'll easily recognize the Dao system above. It's a great series, that I highly recommend, and that I've gotten a lot of inspiration from for building my own campaign. Check it out on Amazon!