With the introduction of the preseason 4 jungle changes, trinkets are now available at lvl1 and can be used after 1:30 in the game. Until now, I've been using the warding trinket to be able to avoid invades from strong counterjunglers. However, the sweeping lens should outscale it vastly if the enemy jungler is of equal early game strength.
As mentioned in the runes section, go for Machete-2x Health pots-Ward when you run armor seals and quintessences.
First buy (750g)
You need the boots asap aswell as the spirit stone for mana and health regen it offers, speeding up your jungling.
This is the core build on jungle nautilus. It offers 30% CDR(+5% from masteries) along with strong amounts of HP, Health Regen, Armor and Magic Resist.
Boots of mobility
will make your ganks so much easier while spirit of the ancient golem
will give you the tenacity you would miss by going mobility boots along with a bunch of health and 10% CDR. Make sure to use it's passive gold bonus effectively by alternating between ganking and farming.
is a strong aura item that you must build instead of your support while he focuses on warding. It gives you Health, Armor while the aura provides the team with Armor, Magic Resist and Health Regen. Despite the removal of bulwark, it is still the best option to build an aegis as it will also give you the active of the locket as you upgrade it along with the valuable 10% cdr.
Active Shield radius:
is the standard anti-ad carry item that you must have during mid/late game as it reduces the attack speed of enemies hitting you by 15% and movement speed by 10% for 1 seconds. Cost was also reduced to 3000 down from 3100 with 3.10 patch.
Spectre's Cowl->Spirit Visage
with the rework on Spirit Visage, it now gives more Health, Health Regen, more MR and also 10% CDR. Although Nautilus can't utilise its passive at its maximum (only the Health Regen part), this item is cost efficient even without the passive. Note that if you need early MR you can just get the negatron cloak early on and then wait until later in the game to decide if you need to build it into an abyssal scepter, a spirit visage or a banshee's veil.
Pretty nice item against double ad carry teams, heavy damage bruisers like jax, rengar, yi. This item has a unique passive: On being hit by basic attacks, returns 30% of damage, before any reductions such as armor, as magic damage
along with 100 armor.
A good item in terms of both damage(burning DoT on enemies standing near you) and survivability(HP+armor). However, your tankiness is decent enough with locket and it's only a personal preferance.
Warmog's is a solid item on every tanky jungler, tons of hp and health regen, especially for nautilus since his shield scales with health (extra 100 hp on it with warmog's).
If you feel your team is lacking vision, this is the perfect buy for you, providing you with 5 wards every time you hit your team's fountain and from which you can have only 3 placed at a time. Also pretty sick hp coming along with this item.
A strong item along with locket, spirit visage for countering of heavy AP team compositions. The shield it provides is not particularly useful for nautilus since he will soak many spells during the course of poking or fighting but this item combines health and magic resist, stats which are all useful for nautilus. With the 3.10 patch, it gives massive health regen for a short amount of time after taking damage along with more mr and health while no longer granting mana, at an extra cost of 250 gold.
Higher damage items
MR shred in a radius along with free AP and MR, solid buy overall vs AP teams when your team consists of a strong mage or is aswell a double AP team.
Strong item overall for damaging purposes, decent health, magic penetration and health percentage damage which will be obvious at team fights if your spells and particularly your Riptide(E) hits most of the enemy team since the damage will be doubled because of movement impairing effects. However, it's quite expensive and should only be considered when snowballing hard. Since Nashor's Tooth is equivalent in gold, this seems like a better purchase due to % damagea and flat health/AP it offers. Go for it as a 6th item when Wit's End isn't optimal due to AD team comps.
If you are snowballing, consider buying this item, making farming really fast, giving you stacking MR on autoattacks and 42% attack speed along with flat MR. After Nashor's Tooth nerf based on jungling nautilus criteria, this is an ideal buy as a 6th damage item since it also steals magic resist from the target(stacking).
This item isn't as strong as it was prior to 3.8 patch, due to the increase in gold cost by 420. The nwe passive added to the item doesn't help nautilus by a whole lot since you should not be building standard mage items.
Other Viable Items
A decently strong item, however based on personal preference I am almost always building Randuin's Omen as my attack speed decreasing item. You can get the 20% CDR from Spirit Visage and you just trade mana for Health.
Frozen Heart Aura Radius:
Another good item on Nautilus with a sick passive for ganks. It has low cost and gives you some Magic resist, Ability Power and Movement Speed along with a great active that sends 2 shadows towards enemy champions and when they reach them, they get slowed down making it easy for you to land Dredge line and the rest of your spells.
Get it early on after your spirit of the ancient golem rush and most likely sell it later on unless you see it as a potential engaging tool against a team without escapes.
If you plan of building Nautilus with an AP core along with tankiness, this should be your starting item as you'll need to have it stacked to make full use of its potential. It gives a very good amount of mana, HP and AP along with sustain in the jungle during level ups when it's still on the catalyst level.
I rarely build it however as i like to build nautilus around resistances.
In some of my games, I sell mobility boots for ninja tabi later on in the game to counter heavy autoattacking teams when I have to soak all the damage. These situations are the same mentioned on the thornmail description.
If you feel like you need even more damage in case you have weak late game heroes like an urgot/corki/mf as ad carry or a mage like brand, heimer, janna, le blanc or zilean, don't be afraid to sell your boots and go for this. It gives ad, attack speed, movement speed and 10% cdr along with tenacity unique passive which is trivial as it doesn't stack with spirit of the ancient golemn.
DO NOT FORGET
During late game make sure to purchase the following for further utility: