This is my first build guide. I am fairly new to LoL (7 months play) but have done a lot of reading and watched top videos on game play and strategy. Other games that I have played intensely include StarCraft and WoW. My build focuses on being dominant early and almost impossible to bring down late game. This build keeps durability while supplying strong damage and some CC.

These runes are fairly standard.

Marks- Magic Penetration: These go really well with your Magic Pen. mastery skill.
Seals- Mana Regen Per Level: Maokai is very mana hungry and needs the regen to be able to continually harass and stay in lane. These runes will give about the same mana regen by level 6 as the flat regen runes.
Glyph- Magic Resistance: Provides a strong early game defense against casters which combines well with the chalice of harmony and mercury treads.
Quints- Flat AP: These runes are where you can very a lot to fit your preference. I take these to maximize the damage from my seeds so that champions cannot farm minions.

9/21/0
I pick up the magic penetration mastery along with improved exhaust. Also reaching the full defensive tier grabbing heal which combines really well with your ultimate. Most people do not believe in heal but I am starting to see it used more especially in ranked. Most teams forget you have it since not a lot of people run with it and can force champions to turret dive giving you the kill instead. I have turned many ganks into counter-ganks using heal and exhaust.

These items are not to be taken directly in order. There are three things Maokai needs in order to be effective; mana, resistances, and ability power. Mana and resistances should always come first unless you are wrecking the other team and can pass the resistances. Maokai needs a huge mana pool for his low CD ultimate. When I blue pill I try and take one mana item and one resistance so that I am increasing the amount of time I can stay in lane and farm. If an enemy champion is getting fed buy items earlier to counter their early game power.

Currently, I am at a 1200 elo with a 90% win ratio as Maokai. My lane partner is always a ranged AD carry on vent (Caitlyn, Twitch, Ashe) and we only have 1 loss from a 4v5. We have ALWAYS been first to push our tower over and have had games with no damage done to our turret. First blood is not guaranteed but is not uncommon depending on how well you synergize with your lane partner. We run an aggressive play style but know when to back off and how to support each other.

A final note to use your passive to stay in lane and recover after enemy harassing. It is more useful then it looks. Feel free to comment!