There are many different ways you can do the rune set up. I like to use the dodge runes instead of health per level runes on the seals, but if you prefer you can do the health/health per lvl runes there and get even higher starting hp(if your an end game player like myself its better with health per lvl). why do I have magic resist runes? well alot of players that I have gone against have been ap, not entirely sure as to why but that's what it is. Instead of magic resist you could put AP per lvl or cooldown runes which will help you tank a bit cause some of the squishy guys will be more scared of your iceball with a bit of ap backing it up, or coming at them 5 times in 12 seconds or so. hp per lvl quints....who doesnt want 150 hp? with the quints ive used hp per/hp, and magic pen. magic pen was fun but for tanking you dont really need it cause your not gonna be focusing ap. Marks of fortitude give you a good boost to starting hp around 27 pluse the 8 or so from the quints 60 from masteries so about 100 extra health off the bat.

I basically went with what I wanted the champion to do for me TANK. So obviously I want to reduce any and all damage coming in and increase my hp/hp regen. Thats why I went 0/21/9.

PROS:

-ALOT of tanking ability
-Lots of hp regen for maintaining a lane
-18% dodge good for those AD ninja's + helps keep you alive longer in team fights
-Well rounded defense and ability to survive, come back into the fight faster.

CONS:

-NOT alot of damage output
-Not alot of kills normally(unless you last hit kill)

With this build, you shouldnt really need to farm. What I usually do with this is i buy a philosopher's stone and a heart of gold, and keep them till I have to sell them to have a slot for my next item. which coupled with the masteries will give you 3 gold per 5, almost doubling your rate of gold income. Also use your passive ability for consume whenever you can or cast blood boil on a teamate and or yourself.