Hi, everyone! I have played league of legends for a period of time. As a member of beginners, I choose the champion Garen because he is easily controlled. Garen is a tank that specializes in early game. In the game, Garen has five abilities, including Perseverance, Decisive Strike, Courage, Judgment and Demacian Justice. Now I will give my opinions from several aspects to share the guide.

Seal of Armor
Seal of Armor will increase defense in lane.
Glyph of Magic Resist
The reason why I choose M. Resist is that Garen can better resist AP champion in early game with the assistance of ability Courage.
Mark of Armor Penetration
Marks of Armor Penetration will do more damage to champions as the game progresses.
Quintessence of Armor Penetration
Maybe you will think that why I use Quint of Armor Penetration instead of Quintessence of Attack Damage. Because the stats of champion will increase with the level including armor, attack and movement speed and so on, except armor penetration, and Garen's abilities are all physical damage, Garen will benefit from armor penetration.

Summoner's Wrath(1/1)
Fury (2/4)
Butcher (2/2)
Deadliness (3/4)
Durability (4/4)

Because the highest level has not been got, I can only share what I am using now. Generally I take Garen at the bottom lane. Although some defensive masteries for health and armor are taken, I prefer to build him as a tank.

Flash
Ignite

Garen has high movement speed at the beginning of game and Decisive Strike can also give movement speed. If we use Flash, we can initiate sudden attack and jump walls, etc. Ignite is the guarantee of killing enemies and restrains champion's health ability of enemy team.

Perseverance (passive): If Garen gets no damage from monsters, towers or champions within 10 seconds, he will regenerate 0.5% of his maximum health. Namely, the more health he has, the more he will regenerate from this ability.
Decisive Strike (Q): Garen removes all slows on him, increase movement speed and silience enemy.
Courage (W): Buffs Garen's armor and magic resist.
Judgment (E): Does AoE damage in range of the hit.
Demacian Justice (R): Does massive damage on enemy's champion, which depends on how much the health remains.
In early game, E is the main ability. Then, points can be given to Q. I suggest Garen attack at top lane or bottom lane. In addition, it is better for Garen to kill opponent champions with teammate and don't kill them by losing life. Be careful to release W because the CD is a little long. Furthermore, if you release all the abilities, but the opponent champion attacks you at this moment, it is possible to be killed.

Starting Items:

Boots of Speed + 3x Health Potion or Cloth Armor + 5x Health Potion
Garen is vulnerable at the beginning of game. Health potions can help him sustain. Besides, the more health is stacked in early game, the more he will regenerate from his ability Perseverance. Boots of Speed gives extra speed which will put pressure on the opponents. Cloth Armor can increase offense to some extent.

My Preferred Items:

Sunfire Cape
This item not only increases armor, but also health. The earlier you get this item, the greater chance you will win.
Warmog's Armor
Besides Garen's ability Perseverance, this item is for health.
Guardian Angel
This effect can only occur once every 5 minutes. Once your champion is killed, this item can revive him at once. It is not a bad option.
The Brutalizer
Getting this item early can shorten CD and increase damage.
Younmu's Ghostblade
This item is synthesized by Avarice Blade and The Brutalizer. There is no doubt that you should get it.

Garen is a good champion to play. Although my level is not so high, I share this report for getting senior player's guide. I think we can play every champion with several builds, not a fixed model. Please give me suggestion and tell me the reason. Thank you.