if you want to play him top, then understand this:
you need to be offensive, take ignite, your set your mastery at 30/0/0 both AP and AD, take amplifying tome, and upgrade it to sheen as fast as possible
you hit your powerspike with sheen. you should be able to get first blood with ignite at level 3-4
chain your soft CC, start with W, your lv1 Damage with Nautilus using a shield will properly suprass most, top laners at level 1, with an excpetion to Darius, due to darius' strong passive (same applies to GP)
i go with Rune page made of this, 3 AS quints, all AD marks, all AP glyphs, and full armor seals.
now this is a high risk high reward, you will get nowhere playing safe and farming with this build, after getting trinity force, take your sunfire, and go tanky from there
wit's end is always an option for a third item. however i always find myself getting abyssal.
always, gank mid whenever you see a chance, unlike most top laners, running to your jungle to grab krugs and recalling would not get you anywhere, you're still nautilus, you're gank/setting up a gank potential is just stupid strong
aslong as you understand your opponent in lane, and know what to max against this, then you're good
don't build nautilus this way, unless you have a background on how to play him and how to soft CC your opponent to negate all damage.
nautilus is just weak and useless against Gnar, and anyone with a Sustain, he's also weak against true Tanks, and point and click harass champions like pantheon maokai ryze, etc
if you're going FULL TANK, then i recommend 3 quints and all marks and all seals to be armor, and flat mr on your glyphs, with a 30 points on the defensive tree, rush a Rod of Ages, or iceborn gaunt, play this build with TP
but keep in mind you will have ZERO kill potential, and the only killing you'd do is either during a gank, or an accidental kill during a teamfight