Hello!

I'm a platinum support main playing a range of supports from senna, taric, pyke etc...
I main Nautilus currently with a 69% winrate :)
I am in the oce server and i've been playing league since season 4.

Pros?

He's a pretty simple support, especially strong with his lockdown potential. Hooks and picks made especially in the late game can pre much determine the game. Low skill cap since the hook hitbox is pretty stupid ngl.
I reckon one of the best lockdown/pick champions available currently.

Cons?
He's really really slow and doesn't have alot of damage.
He also gets punished hard if hooks miss or hit the incorrect targets.
Can't peel well against assassin comps, so itemisation plays a large role.

Aftershock

Pretty self explanatory

Shield Bash

Works well with your w, especially since it is an AA reset

Conditioning

I personally go conditioning works well with armor items you build later

Overgrowth

Based on item build really, if you think you dont have enough health grab overgrowth

Bone Plating

Bone plating does work well, but since most supports and adcs can easily proc your bone plating i generally don't like grabbing it. Against hard engage comps I'd recommend

Unflinching

Against hard CC comps unflinching works well, but since most of the time your frontlining/engaging, I don't find use for unflinching. With the new unflinching rune adjustment, it has become a more viable rune for selection.
"Gain 10% slow resist and 10% Tenacity. Gain up to 20% more slow resist and Tenacity based on missing health"

Biscuit

Just generally nice item, helps you stay in lane for abit longer as well as permanent mana, good against poke lane like velkoz

Stopwatch

Stopwatch builds into Gargoyles and saves you some money off it

Magical footwear

If you don't like roaming as a support, then i'd grab footwear

Approach Velocity

The new adjustment to approach velocity works really well with Naut, in combination with an ADC with with slows/stun, it lets you run faster towards any slowed enemies.
"Gain 7.5% bonus movement speed when moving toward a movement-impaired enemy champion. Increased to 15% if you were the one who impaired their movement (There is no longer a maximum range of 1000 for champions that you have CCd)"

Secondary path is adjustable for your playstyle really

Q: Dredge Line

Throws out a hook in a straight line, dragging the enemy and yourself together
This can also hit terrain but pulls you towards the terrain instead.

W: Titan's Wrath

Shields himself for 2 seconds
Whilst shield is active, his basic attacks deal bonus magic damage
Also AA reset

E: Riptide

3 wave aoe, dealing magic damage slowing all enemies hit

R: Depth charge

Sends out a targetted missle-like charge, chasing the targetted enemy before knocking them up upon arrival.
Also knocks up any enemies along the way

Hook Engage:

Q - AA - E - W(AA)

Ulti Engage:

R - Q - AA - E - W(AA)

Core

Knight's Vow

Knight's vow provides CDR armor and health, but also good peel for your adc.
I normally grab this item if im playing against hard engage lanes like Alistar and Blitz.
Personally prefer this item for most lanes due to its usefulness in long trades at bot.

Zeke's Convergence

I'd grab zekes against squishier backseat supports like Soraka, Nami, Senna etc...
Works well with lockdown potential with its slow, especially with R - Q combo.
I'd grab this if lane had an AP poke

AP Heavy

Absyssal Mask

Abyssal mask is good vs heavy mage teams, generally go for it if your frontline most of the time, works well especially due to your magic damage from spells

Locket of the Iron Solari

Locket for peel, especially for backline, since the shield scales with your bonus health

Mercury Treads

Merc treads for ap heavy, good with tenacity and Unflinching rune

AD Heavy

Dead Man's Plate

Deadmans plate for extra roam potential, if going against a more ad base team, it'll work well with mobis boots and help roam.

Sunfire Cape

Sunfire for the extra bit of damage, will proc on passive autos, E Q & Ulti.
Generally leave for later as it does push waves which your ADC might not like.

Thornmail

Thornmail just for antiheal really, especially since Death's dance on ADC is new metal, its nice to grab this when you dont have an ignite.

Laning

Always try for a level 2 rush, Q + W + Aftershock pretty much guarantees easy trades without you losing lots of health

Your W is an AA reset

An extra bit of damage ontop with shield bash, you do a suprising amount of damage

Hold onto hooks

Generally if you don't feel comfortable going for hooks, you can always bait them out by walking towards them.
Also sometimes its better to engage with your R instead as it ensures that a hook will be landed after they are knocked up.

General build

5th item slot is situational, depends on comp your playing against, refer to item building. If unsure just grab a Gargoyle's Stoneplate

Vision control

I always leave the 6th item slot empty for control wards, personally feel like vision is more important and lets you make easy picks if you can co ordinate with team, especially in late game where a single pick can force a 4v5 and win the game