Amazing start vs AD based top laners. Reduce incoming damage and regen for days.
Dorans blade is insanely risky on Garen since he can't sustain well with it due to not auto attacking much in trades and having a generally slow clunky auto that you cant use to keep up as well with other champs who auto-attack more effectively for dorans sustain. That said the 80 hp and 8 flat AD can work quite well in trying to all-in people early. This is a good pickup if you expect the enemy champ to be a low-sustain lane who would be susceptible to Garen's level 3-4 all-in.
This is a good pickup against a select few lanes, mostly auto-attackers who deal magic damage and just not physical. Champions that come to mind are things such as Jax and Teemo.
You can Take this set if you get counted picked by a range champion, to let you move in and out of range of CS quicker and have a few potions to sustain with.
You want the Magic Resist and Tenacity vs Double AP comps or an AP laner. The MR helps reduce their damage and most casters have some CC so the tenacity never goes to waste. Usually you want these late game no matter what unless you're against a 4-5 man full AD team.
Armor and auto attack reduction vs standard AD tops or fed AD Carries. Armor reduces incoming physical damage so it's pretty easy to see why this is so good. These are generally good in lane and are good against heavy AD comps. If the enemy has fed melee ad carries such as Tryndamere, Yasuo, or Master Yi these are good to have.
These don't provide that much compared to the other two options. You run a little faster and are harder to shut down with slows, but the magic resist/armor and the other passives the boots give are worth a lot of gold and are hard to give up.
Brutalizer is super ideal for an early damage item. Combined with flat ArPen runes and the Penetration masteries in 21 offense, it's a pretty good damage item on Garen in general and does work in team fights.
You can rush Ghostblade if really fed and combine it with Infinity Edge for insane early and mid game damage. You can also pair this with Black Cleaver for awesome combined flat penetration results. You can sub out statikk shiv for this instead against tankier teams (armor stacking).
Get last whisper if every one the enemy team is stacking armor or ultra late game when you need more damage.
Shiv is really good on garen since it makes your burst higher with the shiv proc, the movespeed is solid anti-kite power, the crit chance works with your abilities and if you're running 21 in offense masteries you'll have extra magic pen to keep the proc relevant. The main downside of this item is its build path leaves a bit to be desired for Garen but the completed item is great. Combined with Infinity Edge or other crit items and it becomes insane. I would mostly build Shiv if you're getting Infinity Edge since those two work well together, but skip over it if you're stacking penetration instead.
Infinity edge works well on Garen if you have arpen runes + 21 offense + and finished black cleaver. It's really insanely expensive though and the damage is amazing but you have to be really far ahead to make it. Works well combined with Ghostblade, or shiv. Still strong combined with black cleaver, though a bit less so since the % crit chance nerf.
This is actually a good choice on garen but its really expensive. Can be a late game item vs AP Comps with 1 or 2 core CC's you want to circumvent.
Get this if you need Magic resist beyond merc treads as its the ideal MR+DMG item on Garen, tanky damage, great shield, etc.
Easily the best armor item in the game in my opinion. Get this as your core armor item. Rush wardens mail vs auto-attack lanes and upgrade to randuins after you have your core damage items. Use the active in team fights for anti-kite! Never skip this!
Not worth rushing anymore but you can still add this on late game if you need more armor and health, since the passive is technically better late game than it was before and it's still a cheap buy. If you're really behind you can get this + randuins early and delay your damage build till later.
Warmogs has a place on garen now after the passive buff, it's not necessarily the best general defensive item but more raw HP and the regen passive of its own basically makes your late game regen very high, its worth considering this item against teams with a lot of flat true damage, or if you think the game will go really late where you will be able to take advantage of garens new late game regen quite to good effect. You can tank poke for your team and heal it off incredibly fast with this and garens buffed passive after level 16. It's worth noting that I still think warmogs isn't ideal though.
Spirit visage is really good now on Garen also because of his regen passive, it's more of a late game item than an early game item since the regen doesn't become truly relevant until level 16 but it does become very strong then. If you make a magic resist item late game, this is probably better than banshee's veil now against teams that aren't directly countered by spellshields.
This is the better magic resist item in the early/mid game if you rush an MR item to completion, its the better late game Magic resist item in the late game if a spell shield is unusually strong against the enemy team (think huge initiation CC's or 1 rotation burst combo reliant champions).
Works well as your core MR item against teams with lots of AOE magic damage, might be worth making if your team cant get it early enough.
Works well if you need a little magic resistance, but also need more armor, can replace the slot used for spirit visage.
DO NOT BUY
Pretty much useless. Low AD, health only for defense. You cant proc the passive during spin. super expensive. basically useless.