Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
Just wanted to post the items, runes and masteries for you. you can read about garen and how to play him in the other guides.
Just jump in there right after your tank initiated. Silence morons, and whirl carries according to your team focus chain.
15% Magic penetration is for your ult and your fire cape. It's just 1 point, and worth more than the 2 armor pen you'd get next to it.