So I bought Nautilus but I'm having a hard time making a good build for him. ( In Dominion )
I build him tanky yet he is getting squished pretty easy , what am I doing wrong ?
Masteries 0/21/9
Runes - Armor Pen , Ressilience and Warding
Item Build - Boots ( Ninja Tabi/ Mercury ), Shurelya's Reverie , Frozen Heart the if they have 2 or more AP Force of Nature , Frozen Mallet and depending if I own or get owned a defensive item or Rylai's Scepter or Abyssal Scepter
Also what skill sequence is good ? I try to max W first the E and finally Q.

Should I screw the tanky part and just go full AP ?

I would not start with utility items on him.
Ring, CDR boots, Belt. Armor\Mres (mail\negatron)
Another Belt.
Then you can go Rylai or Sunfire or Frozen Mallet.
Add Tornmail vs AA-heavy team.

I do not suggest FoN bc healing is reduced in Dom and %HP healing is hard to use effectively (no Warmog)