Garen is possibly the tank with the most damage, or the dps with the most health. Simply with this build, he will have over 3k hp with all his items, and up to 75% reduction of physical damage.
He has alot of sustained damage and fighting presence with his Q-W-E combo, and will take noticably less damage. While there is an argument to getting life steal, i find that this works better.

Garen isnt as dependant upon items as you think, so there is alot of versatility. However, there will also be controvery over the best order.
Many people will be enraged that I take a Doran's Sheild over boots and 3 pots, but with his passive, you dont really need the regen from pots, and a doran's sheild is a great choice.
Many people will also question the use of the boots of swiftness. Well, think of it this way. Anything boots give you can be supplemented by other items, except flat speed. This will really give you an edge while escaping, and also chasing. Combined that with your Q, and possibly ghost... only yi can top you.
This build is designed to give you the best tankyness. Your mallet will give you health, and the rest is magic resist and armor, focusing on armor. If you feel that you need more magic resist, drop the sunfire for another resistance item. Possibly quicksilver sash. But, if you dont really feel pressure from magic dmg, take a guardian angle instead. You wont be dieing much anyway, but it still helps out. A little magic protection, but also armor.

There arent really any great summoner spells for him. I just feel that this gives you the best versatility, with both chasing and escaping.