Disappointed.
Your Mobaguide, if it can be called that, is lazy at best. You fail to discuss Garen's strengths and weaknesses. Your build order is, again, lazy and unoptimized. And then the thing that seals your guide's fate as uninspiried and worthless to people seriously looking to pick up Garen is the fact that you just lazily threw just about every champion in to the No-Threat category.
What you've put up, to continue my critique here, is of little use at best, and dangerously unhelpful at worst. I say this as a Garen main. You HAVE to honestly discuss a champion's strengths AND weaknesses. Garen is not invincible, and your build leaves him with almost no tank stats whatsoever. For Garen, that is CRIPPLING. He is, at best, an opportunistic engager. #2. If he has to be the one to engage, he needs those tank stats to survive the onslaught.
I'll give you kudos for the Boots of Swiftness + Furor. That's something that I've not seen any other Garen pick up besides myself, and it does help alleviate some of his problems with sticking to more mobile targets.
But if you're gonna make something called a guide, it needs to have considerably more substance that what you've put in right now. Why should he go 12/18/0 over something like 12/0/18? Or, if he's building damage like you have, why not got 18/0/12 or 18/12/0? Which Keystones does he synergize well with? Why build X item over Y? When should he pick up certain items? What's his core set?