Hello everybody, this is my guide for Off-Tank Garen.
Summoner spells

Ghost fits perfectly with your q skill and with your boots of swiftness you have a rly nice movement speed. Exhaust i take on every melee dps champion, the best choice for them i think.

runes

marks of desolation for armor pen
seals of evasion for more tankyness and increases your bonus from masterys
glyphs of focus cause cdr is needed by garen and finally
quintessences of fortitude for even more early tankyness

items

i start with ruby crystal cause garens passive gives you enough health regen. frozen mallet for slow and health for more tankyness. I think garens dmg is early enough but if you wnat to go for even more get a brutalizer and sell it then for your last item. Brutalizer is a great item for garen: dmg, armor pen and the cdr. Next is Sunfire cape; it gives you armor, more health and the passive is great with e skill. Now go for atmas cause you have by now anough life for the ad boost. atmas gives you also more armor and critical strikke chance. This item is also quietly cheap. Now go for a warmogs for a greater boost on atmas and more tankyness. if the other team stackt a lot of armor or you think you are enough tanky go for last whisper instead of warmogs. Infinity edge is a great last item, it increases your ciritcal strike chance from atmas, your dmg and now your critical strikes are 250% of your ad.

masterys

i choose this masterys for tankyness and a few points on offense tree for critical strike chance, better exhaust and a bit cdr. 1 point for a better ghost, skip this if you take flash instead of ghost.

farming/laning

garen is great at early game, you can play aggressivly. it is all situation dependent. if the enemys are rly defense use ur q and e skill consequently on creeps, it costs nothing. dont use on full hp minions cause your e skill dont is long enough for full hp minions.


fights

you are tanky enough to initiate fights. wait for the right moment, run in with q, try to scielence the feedest mage, if hes not there or too far away focus the next squishy. pop your e and and your shield. remember you can use shield wihle you are circling. it is also possible with your q, if garen stops his next atk will be instantly scielence.
use your ult whisely; dont waste it on full hp enemys but also dont try to steal kills with it.

some people maybe think now a madreds would destroy this build or that i dont stack any magic resistence. madreds is expensive and the most dont use madreds in their core (like ww or ad kog maw). Other like Yi will try to get it after they notice that you have a huge amount of life and also deal dmg as hell. When You got this amount of life early/mid game is past and there wont be a 1on1 anymore. If they focus you in team fights you die but it takes a lot of time and your team win this fight. If its not ww or some other off tank with madreds ask your team to focus them (kogmaw,ezreal,yi...)
MR is with that amount of life unnessecary i think. you have your w for shield and a mage cannot use madreds. and you have your silence that they cannot use spells for an amount of time they dont survive probably

thank you for reading, pls do not down vote without comment