My items are for maximum GP5 at early game and ultra tank at late-game. You start with a Ruby Crystal, giving you health for the start. As soon as you get 350/700 gold recall to guy heart of gold/and boots. This will maximise your GP5. When you reach 800 gold recall and buy your Philosophers stone. If you have spare gold buy a sight ward. Whe nyou get 765 gold recall and buy your Kage's lucky pick. Whenever you have spare gold upgrade your boots/start on the next item and get wards.The Avarice blade is optional, but i reccomend buying it. Whether to buy Thornmail or FON depends on if they have more AP or AD champions (FON is for AP and Thornmail is for AD). Once you have either your FON or thornmail, Sell your Avarice blade and buy the other item. After you have both FON and Thornmail, sell your Kage's lucky pick and build your first warmogs. At this point, you may sell any of your GP5's except Philosophers stone. Once you have bought your first Warmogs, Buy your Shurelia's Reverie. Your last item is debatable, but i usually buy either a second Warmogs, or Rylai's Crystal Scepter. Once you have these, you are extremely hard to kill and have massive HP regen!

This is just how i build my Tank nautilus and it DOES work in ranked. Please try it and modify it to fit what works best for you!

For summoner spells, i always take flash, and either Teleport or Heal.
These are just what i am best at using, and can be exchanged for any other support-style Summoner Spells.

For runes, I usually get GP5 seals and quints, MR Glyphs and Magic Pen Marks.
The Seals just maximise your GP5, but can be changed for flat armour or armour per lvl seals.
I reccomend you to use MR glyphs, because they just help you take less damage, but can be exchanged for Mana regen or flat AP Glyphs.
For marks, i haven't determined what is best, but i use Magic Pen.
Getting GP5 quints on a support/tank is DEFINITELY the BEST POSSIBLE option, but still can be exchanged for nearly anything.

In conclusion, this is just my build, and what works for me.
You can modify my build, re-arrange the items, get Armour seals instead of GP5, Buy different items. Just find what suits you best!

Please +vote my build and show it to your friends!