Nautilus is a tanky ap carry, i like to build him HP/AP because his Titan's Wrath stacks very good with more health.

I build a 21/9/0 build with nautilus because of the items i buy ingame makes me tanky without having to spend points in Defence.

For runes i take flat AP Glyphs, MP5 seals, Magic Pen marks, and flat AP Quints.
With these runes you will hit like crazy and still have enough mana regen to let you stay in lane.

For my summoner spells i pick Heal and Flash.
Flash is a must have for almost every champ.
I pick heal because it will help you survive in the early game, although i feel it lacks usefullness in the later stages of the game.
If you dont want to use heal Cleanse or Teleport is also great choices.
If you feel like playing more offensive you can pick Ignite/Exhaust, but this is not something i would recommend since ur role is to take damage and survive.

Since you have the tank role, you goal is to jump in and make the situation for your team as good as possible.

You should start with Using your Q to jump in to an opponent, then use your E for maximum damage.

Use your ult whenever you can to knock out those squishy massive damage opponents.

Your W will keep you alive longer so use it whenever you need.

CRUCIAL: Dont forget to use your passive! if u you can land a melee attack it may help you win.

Just play defensive and farm as much as you can, but dont be afraid to engage after you've hit level 3.
Just remember: Never go for a kill if it means a sure death for urself.

Depending on what lane you are in and how the gae is developing you can try to gank.
Nautilus is an excelent ganker with his stun, slow and pull abilities.

You're crucial to the survival of your team.
Your role is to jump in to the enemy team and do AOE dmg, although you have som excellent kiting abilities.

Please try this build in-game, and if it works for you why not vote :)
Also this is the first build iv'e made so aome comments telling me how i should improve would be nice.

Thank You.

Imakillyo
EU Nordic