Introduction
From what I can tell, a lot of people still recommend building
Garen as a tank or an off tank who only gets 200 attack damage. Sure he might be hard to kill, but it doesn't matter if you can't kill the enemy quickly and effectively. that's what this build is for: a build that gives you nearly 300 attack damage while still being bulky. And for team two, you can still play the role of the tank, but you get 330 attack damage! That's AMAZING!
The numbers lie!
Some of
Garen's stats are not correct.
They should be:
Team 1:
Attack Damage 292.41
Armor 150.29
Magic resist 115.91
Movement speed 462.15
Team 2:
Health 3703
Hp5 64.3
Attack Damage 332.21
Armor 161.9
Magic resist 162.8
Movement speed 462.15
Ok, how about those movement speed quints?
I used to question using movement speed quints too, But before using them it seemed like I couldn't quite reach my target before they escaped. Having the extra movement speed makes it easier for you to:
- catch your target.
- escape after taking down a turret/inhibitor.
- makes getting around a lot faster (especially with [Decisive Strike]).
Why the heck do you have 22 points in utility?
I run 22 points in the utility tree for a couple of reasons:
- The bonus experience lets you get ahead in levels quickly, so you can crush the other champion (or two) that are top.
- The extra gold at the beginning of the game helps you stay in lane for much, much longer.
- The cool down reduction increases your damage output quite a bit.
- The other trees help you most early game, but the utility tree is useful through late game.
The Skill Sequence
Below I have
Garen's skills and a blurb on each of them.

(Innate): Garen will regenerate 0.5% of his maximum health per second after not receiving damage for 7 seconds. The regenerative state will stop if Garen receives damage.
Perseverance is what allows you to stay in lane forever. If you're ever low on health just stick by your tower or jump in a bush for a bit. It's also nice whenever you are running around.

(Active): Garen gains bonus movement speed for 4 seconds, in addition his next melee attack within 6 seconds will deal physical damage and silence its target for 2.5 seconds.
No cost
Cooldown: 12 / 11 / 10 / 9 / 8 seconds
Total Physical Damage: 30 / 45 / 60 / 75 / 90 (+1.4 per attack damage)
Bonus Movement Speed: 15 / 20 / 25 / 30 / 35%
Decisive Strike is pretty much the only cc
Garen has, but it's all he needs. At level 18 one hit from this would deal 554 damage, but with
Trinity Force it deals 787. Impressive, no?

(Passive): Garen's armor and magic resistance are permanently increased by 0.5 every time he kills an enemy unit. Garen can gain a maximum of 25 armor and magic resistance.
(Active): Garen places a defensive shield on himself, decreasing all damage taken by a percentage for 3 seconds.
No cost
Cooldown: 30 / 27 / 24 / 21 / 18 seconds
Damage Reduced: 20 / 24 / 28 / 32 / 36%
Courage is the move that makes you unkillable. The Damage reduction is amazing in team fights, and it's passive makes you much tankier early game. Getting one point in this early lets you max its passive earlier, thus making you harder to kill.

(Active): Garen rapidly spins his sword around his body for 3 seconds, removing all existing slows and reducing the duration of new slows by 50%, plus dealing physical damage to nearby enemies every half second. Minions and neutral monsters only take half damage from this ability. Garen can deactivate Judgment early by activating the ability again after 0.5 seconds. Garen cannot use Decisive Strike or Demacian Justice while Judgment is in effect. Judgment's damage can critically strike, in which case, only the bonus damage will be multiplied.
No cost
Radius of AoE: 330
Cooldown: 13 / 12 / 11 / 10 / 9 seconds
Physical Damage Per Second: 50 / 90 / 130 / 170 / 210 (+1.4 per bonus attack damage)
Total Physical Damage: 150 / 270 / 390 / 510 / 630 (+4.2 per bonus attack damage)
This is
Garen's bread and butter skill, and is also his main source of damage. Maxing this first ensures that the damage you deal is always head of the others. Late game,
Judgment would deal a total of 1558 to one enemy, without critical strikes! Remember that this is an AoE ability.

(Active): Garen brings down Demacian Justice on his opponent, dealing magic damage, plus additional magic damage based on how much health his opponent is missing.
No cost
Range: 400
Cooldown: 140 / 120 / 100 seconds
Magic Damage: 175 / 350 / 525
Additional 1 Damage per: 3.5 / 3 / 2.5 target's missing health
Demacian Justice is your kill secure. It can kill any champion once they have less than 25% hp at level 3 and it is a great way to start a killing spree.
Edits
Edit 1: Took out my ad for ap Nasus. made the team fight more realistic.