Hello! I'm some silver pleb who played too much Maokai for the past few weeks and decided to make a guide on this because I was bored. Hope you enjoy!

- Primary Tree

Aftershock - This will be your main keystone as it can proc on both your Twisted Advance and Nature's Grasp since those will be your main engage tools.

Font of Life - Bone Plating is also good on Maokai but you can consistently proc Font of Life with Bramble Smash and Sapling Toss to add more healing to your team. It can also serve as a notification that someone has been hit by one of your saplings if you place them in bushes as pseudo-wards.

Conditioning - After 10 minutes this allows Maokai to become even tankier with more resistances. Second Wind is another option if you're facing a poke-heavy lane such as Caitlyn and/or Zyra.

Overgrowth - More HP = Good. However that doesn't mean Revitalize isn't good either. Take Revitalize into a poke-heavy lane instead of Overgrowth.

- Secondary Tree

Triumph - This baby here can save you in early dives or big teamfights lategame since you can heal up for a massive amount and remain a constant threat.

Legend: Tenacity - With the recent buffs to this rune it can now basically replace Mercury's Treads and allow you to buy Ninja Tabi or stack even more Tenacity.

Turbo Chemtank - Simple engage tool that allows Maokai to run at Mach 5 to get in range for a Twisted Advance.

Spirit Visage - This works well with Maokai's Sap Magic to allow him to heal up for a massive amount.

Warmog's Armor - Gives you more HP and makes you beefier. Also lets you quickly heal up in between skirmishes.

Oracle Lens / Elixir of Iron - Your job as a Support is to ward objectives and make sure Akali isn't sitting in a bush waiting to murder your Vayne. Elixir of Iron should be bought if you can't afford anything before a large fight is going to start or lategame when you're at max build for more tankiness.

Flash - Essential on nearly every champion. Maokai can use this to escape or create a gap closer to engage.

Exhaust - Prevents your backline from being blown up by Zed. Simple and easy.

Ignite - Used to secure kills early on or to counter sustain champions such as Soraka.

Engaging with Maokai should be fairly simple with his point-and-click Twisted Advance root. Simply run up to them and press W.

Turbo Chemtank - This will help Maokai cover a larger amount of distance between him and his target with the movement speed boost, and the slow from it will further increase the amount of CC he has.

-Basic Engage : Twisted Advance + Bramble Smash towards teammate(s)
-Basic Engage #2 : Turbo Chemtank + Twisted Advance + Bramble Smash
-"I'm Rengar" : Sit in a bush with Saplings, Twisted Advance when a target gets close enough -> Bramble Smash into Nature's Grasp
-Ultimate Engage : Nature's Grasp -> Sapling Toss onto target -> Twisted Advance -> Bramble Smash towards your teammate(s)
-Late Ultimate Engage : Twisted Advance -> Nature's Grasp -> (Q) / (E)

We start with Sapling Toss and that's your basic form of poke and it can be a used for vision in a bush when you don't have a ward up. Twisted Advance is maxed first so the root duration is longer and the cooldown is lower. Bramble Smash is last since it only increases the damage dealt and you will use it instead to knock back rooted enemies into your team or away from your backline.