This garen is shockingly good, with the ability to do in game damage. The Warmoggs, Frozen Mallet, Sunfire, Atma's has amazing synergy. The Ionian boots are for the cooldown reduction and i feel theyre the best boots for him, especially at that price. His high ammount of life allows him to suck up the nukes while courage and spinning through the team with his massive damage. Lastly i get an infinity edge due to its synergy with the judgement and atma's as you see above a 48% chance to crit why not add some extra pow behind that. The only downside to this build is it is pure life with no real defense besides runes and masteries so be ware.
I got damage runes with armor and MR to be affective beginning game, as we all know garen is beginning to late game stomp. :)

Pros:
Amazing ammount of life
Great Tank
Great Damage
Courage is Great source of Defense

Cons:
No Resistance Balls to the Wall
Countered by Madreds so target their dps silly.
XinZhao rapes your face cause he is op for no reason :P

GLHF hope this build works for ya.