Do not do this against hard counters such as Quinn or Gnar
This build is mainly for fun but is also extremely strong. However, this build falls off pretty quickly as soon you will find yourself getting melted pretty quickly if you can not close the game fast enough.

Go Adaptive Force for the first two then either health or required resistances against a poke lane.

The main option here is and . Use these spells to destroy your lane and snowball out of control. However, can be switched with if the enemy has a lot of mobility or is ranged (like )

Pretty normal stuff, R->Q->E->W
Max ult for the lower cooldown and base damage.
Then Q for the next most damage and for poke in lane.
E is for the armour shred.
W for defensive capabilities and tenacity (No damage means it's bad, right?)

is the go-to first damage item on Garen because of its verstile stats.

are situational however, Mercury's Treads is what you will be buying the most.

adds to that upfront burst to catch enemies off guard.

increases Garen damage and chasing power/stickiness. This can be replaced with Duskblade if the enemy team has no mobility in general.

Maw of Malmortius is great against heavy AP team comps or simply to complete Hexdrinker.

's slow, damage and ward control is great for camping in bushes.

Edge of Night is great against CC heavy teams so that you can run in without looking like an idiot and dying.

Both Mortal Reminder and Lord Dominik's Regards are great on Garen for that extra damage on tanks and squishies alike. The Grievous Wounds passive is also great against champion like Illaoi or Darius.

This item is great for when you are ahead so that you can stay in the fight that little bit longer or stall for your team.

Death's Dance is another great survivability item on Garen. The Area of Effect heal synergises well with Garen's E's single target damage.

is another great bruiser item to help Garen survive in teamfights while still dishing out large amounts of damage.

Righteous Glory is not a damage item, however, that burst of speed can almost always tee a kill.

and can be slotted in after Stormrazor if the enemy team is slightly tankier than normal. This build still does quite a lot of damage.

is the best for damage on Garen. It compensates for Garen's lack of mobility while giving him extra damage as well. Note: Try to not to rely on Predator for gap closing after iniating a trade. The enemy will most likely CC you and you will end up creating a farther gap then if you would have run at them and wait for Q cooldown.
{icon=Cheap Shot] and adds more damage.
is great for sustain in fights but can be swapped out with [Ultimate Hunter] if desired].
is great in teamfights and for tower dives as the extra health usually means the difference between life and death.
helps with executes via or simply anything at all.

Excellent against teams with a lot of skillshots/CC. Phase Rush gives easy maneuvering and gap closing of enemy mobility. Absolute Focus can be switched out for Celerity for extra speed and to help chase fleeing enemies.

This is for when early laning phase is harder or against a lane like Teemo.

This is amazing against lanes which you will 100% win (player dependent though).
When done correctly, you can Q then R instakill someone.
Falls off and hard to come back.

Laning phase is heavily reliant on your knowledge of matchups so if you don't know how to play your lane, you will fall behind very quickly as you are not building tank. (It's Garen right so how hard can it be?).
Generall speaking though, you'll want to poke with Q (then run into a bush to drop minion aggro) until the opponent is low enough for you to all in.
Try not to push the lane in order to give yourself room to chase the opponent down.

In teamfights you'll obviously want to go for the squishy backline, however, you will want to wait for the fight to start and cooldowns to be blown so that you don't get one-shot when you eventually go in.