Is this a good build for Garen?

Yeah he needs to dual wield and wearing different shoes is a new meta.

You definitely need both boots. And the dual boosts his ult damage.

Builds are supposed to be dynamic. Don't just copy something that a 'pro' uses without taking into account why he built it. The Garen build you posted might work against some team comps but not others.

Garen is nothing without DFG

For some reason, I laughed pretty hard at this.