I have recently built a new Warden and just got to level 12. When I trained up at a Warden Trainer, I got 9 new Mastery skills (Fist & Fist, Spear & Spear, Shield & Shield, etc). I have them on my skill bar, but they are all grayed out and say that I can't use them. I thought that they might only light up when I am in combat, but they don't even then! So what are they supposed to do?
For these to work you first have to trait so many of the red blue and yellow to activate them. 5 of any color give you access to all of them. At your level you cant do this yet...but you will. Look at your class traits and check out the bonuses for traiting more of the same line. Later you with practice will grow to love and rely on these. They let you fire off gambits a lot faster. When you can use them you will be able to build a fist shield in half the time and dont have to be in mele range of the target to do it.
Change your point of view and change the way you perceive everything.
Masteries are used to simplify the Gambit building process. They add two builders so that you could potentially and theoretically build Gambits twice as fast. They have cooldowns unlike our regular builders so you would typically create rotations to use them effectively. Check out this guide on how to use your masteries effectively.