hello hello

There are many different rune pages you can run with Maokai. This one is probably the most standard one.

The magic penetration marks can be switched out with a few different things such as attack speed or flat ability power, but it's generally better to just have this penetration.

As far as seals go, there really aren't any other optimal choices, you need the armor to survive in the jungle and you need it if you want to gank without dying in two hits.

The magic resist glyphs can be swapped out for cooldown reduction if the enemy team doesn't have a source of magic damage or you could also get scaling magic resist glyphs, but those are generally not as good on maokai as most of your ganking is done in the early levels (which I'll talk about more later!)

The movement speed quints are a must in my opinion. You need to be very active in the early/mid-game because those parts of the game are your strongest points. Having extra movement speed will help you with ganking and getting to places faster, may it be objectives, lanes or camps.

Masteries on Maokai vary depending on your playstyle. I feel like this is the most generic mastery page you can run on him and I really recommend using it.

As far as the 21 points in Offense go, you'll get the increased clearing time with butcher and will help you regenerate off killing units with feast. You also have increased cooldown reduction (very important stat on Maokai) and the utility masteries like Expose Weakness.

The 9 point in Defense are the basic jungler masteries. Increased health, reduced damage taken from neutral monsters, etc.
Tanky Masteries suggestion By IcyAuron

You usually want to start by getting sapling toss at level 1 and stacking them on the buff you're starting at (I'd recommend Frog!). After that, make sure you get Arcane Smash as that will you be your main clearing ability and damage ability. Once you're level 3, get Twisted Advance so you can start ganking!

In terms of spells to max, you start by maxing your Arcane Smash then you follow up with your Twisted Advance and you finish off by maxing Sapling Toss. Make sure to get your ultimate at levels 6, 11 and 16.

Summary:

Level 1 : Sapling Toss
Level 2 : Arcane Smash
Level 3 : Twisted Advance
Level 4 : Arcane Smash
Level 5 : Arcane Smash
Level 6 : Vengeful Maelstrom
Level 7 : Arcane Smash
Level 8 : Twisted Advance
Level 9 : Arcane Smash
Level 10 : Twisted Advance
Level 11 : Vengeful Maelstrom
Level 12 : Twisted Advance
Level 13 : Twisted Advance
Level 14 : Sapling Toss
Level 15 : Sapling Toss
Level 16 : Vengeful Maelstrom
Level 17 : Sapling Toss
Level 18 : Sapling Toss

You're going to need flash on Maokai, there's no reason to get anything else. Flash is just such an overpowered summoner spell, especially when you combine it with your Twisted Advance (W). You can get some really good engages off by flash w'ing a carry and knocking them in to your team while having your ult up.

Smite is required for jungling, the objective and buff control it provides is absolutely necessary.

Sap Magic (Passive)

Each time a champion near Maokai casts a spell, he gains a charge of Magical Sap. When he has 5 charges, his next melee attack drains energy from his target, healing Maokai for 7% of his maximum health.

This passive is extremely strong, it's great for sustaining in fights and in the jungle. Make sure you keep track of your stacks and auto-attack something once it's at 5 charges to gain a huge amount of hp back (huge because you're going to have Spirit Visage!)

Arcane Smash (Q)

Maokai releases an arcane shockwave. Enemies within 100 units are knocked back and all affected enemies take magic damage and are slowed for 1.5 seconds.

MAGIC DAMAGE: 70 / 115 / 160 / 205 / 250 (+40% AP)
SLOW: 20 / 27 / 34 / 41 / 48%

The damage this spell deals is really good but the slow and the knockback are what make it amazing. It's really important to use this properly when ganking or teamfighting. You can use it to cancel ultimates that are channeled (Warwick, Katarina, Malzahar, etc.) because of the knockback. You can also use it to push enemies in to your team or just straight up slow them for 50% (which is pretty huge by the way).

Twisted Advance (W)

Maokai transforms into a cloud of arcane energy that quickly travels to a target enemy, deals magic damage and roots it. Damage is capped at 300 against minions and monsters.

MAGIC DAMAGE: 9 / 10 / 11 / 12 / 13% (+3% per 100 AP) of target's maximum health
ROOT DURATION: 1 / 1.25 / 1.5 / 1.75 / 2

This is your main form of crowd control. The root duration is pretty good, and it will allow you to setup for an Arcane Smash + Sapling Toss combo. The % health damage is pretty good as well, depending on who you use it on.

You're generally going to want to use this on carries in teamfights OR on the enemy frontline, depending on your playstyle. Either you peel for your carries by rooting the targets going on them or you dive the enemy carries and root them in hope of a follow up from your teammates.

It's also really important to note that you can dodge channeled ultimates (Karthus for example) and any other skillshot if you use your Twisted Advance when it's about to hit you. I'll have a picture/gif demonstrating what I mean in a later portion of this guide.

Sapling Toss (E)

Maokai flings a sapling that deals magic damage on impact. The sapling wards the nearby area, and will chase enemies that approach, exploding to deal magic damage and slowing enemies hit by 50% for 1 second. Saplings last for 35 seconds.

MPACT MAGIC DAMAGE: 40 / 60 / 80 / 100 / 120 (+40% AP)
EXPLOSION MAGIC DAMAGE: 80 / 120 / 160 / 200 / 240 (+60% AP)

It's really important to land this on the target you're going for as it will deal a fair amount of damage but most importantly it will slow their movement speed for 50%. Generally, you want to Twisted Advance the person, throw your sapling on them and knock them backwards with your Arcane Smash. By doing this, they should be rooted and slowed for a good amount of time, which should give your teammates time to follow up and take out the target without a problem.

Something that is overlooked about these saplings is that they last 35 seconds, that's half of your initial warding totem. Make sure you use these saplings as a form of warding! You can check bushes and even leave them in the enemy jungle to know where they are!

Vengeful Maelstrom (R)

Maokai creates a magical vortex around himself, protecting him and allied champions by reducing damage from non-turret sources by 20% for a maximum of 10 seconds.

When the effect ends the absorbed energy is released, dealing magic damage to enemies within the vortex's range, plus bonus magic damage based on the damage stored by the damage reduction effect.

MAGIC DAMAGE: 100 / 150 / 200 (+50% AP) (+2 per damage absorbed)
MAX STORED DAMAGE: 200 / 250 / 300
MAX TOTAL DAMAGE: 300 / 400 / 500 (+50% AP)

The fact that Maokai's Ultimate follows him around is absolutely absurd and overpowered. He receives 20% less damage taken while it's toggled and can also detonate it to deal a good amount of damage (especially at lower levels!) You're going to want to keep this on for as long as you're teamfighting. Try to soak as much damage as possible while having it enabled and make sure you detonate it while people are within range of the vortex, to get the most efficiency of it.

Ganking is a really important aspect of the game when you're playing Maokai. Farming won't make you a monster and you really need to have good presence early game and mid game as you really fall off late game, especially if you're not ahead. That being said, I usually go for a gank on mid/top at level 3, depending on what champions I have on my team.

It's also good to keep in mind that even if the lanes are pushed to the enemy tower, it doesn't mean you can't gank. If those lanes really are pushed to the enemy tower, guess who's getting ganked? Chances are that your lane will get ganked, you can set up and wait in a bush to countergank, they will be surprised and won't expect you to be there so you'll be at an advantage.

The best way to get good with ganking/counterganking is to have wards up in the enemy jungle, you'll be able to know where they're going to and just knowing what part of the jungle they're in is a huge advantage for you and your team, it will give your teammates the chance to be more aggressive if they know he's in the top part of the jungle and they're in the bottom side. Good wards to place in the enemy jungle are usually around their blue buff and at their Razorbeaks.

Knowing how to teamfight is really important on Maokai, and it's different every game. There are a few factors you need to keep track of and be aware of in your games.

First off, you need to know what kind of a team composition you have, if you have a poke composition (this would have champions like Varus, Caitlyn, Corki, Jayce, Nidalee, Syndra, etc) then you want to wait for your team to deal some damage before engaging. At that point you'd probably want to dive the lower targets or the more vulnerable targets (those with no escapes) and make sure their deaths are prioritized.

If you're running with a dive composition (this will usually have assassins like Zed, Fizz, Talon) you want to catch a target and nuke them, so you wouldn't really be peeling for anyone, you'd be going for a dive on the enemy carry (person who's the strongest on their team), probably the ad carry or the mid laner.

If you just have a standard team composition then chances are you're going to want to peel for your carries, the best way of doing this is just rooting and slowing people who are trying to dive them, it's a really efficient way of playing and is generally the safest way to play as well.