What do max first, e or q? I'm guessing e.
On Maokai, max Q, then W, then E. Mana cost on E scales with points so its best to keep at 1. It's great for scouting since the cast range is gigantic and for picking off backline creeps when zoned by pokers. Q is great for harassing melees and clearing the wave, and costs only 45 mana so once you get Catalyst (and possibly a second Doran's Ring) you can clear waves very easily. W's cooldown and damage improve signficantly with points so it goes second.
Early game is mostly about avoiding ganks, CSing as best as possible, and helping set up ganks (immediately call for a gank if they push without wards, Maokai has immense lockdown with CC on Q, W and E). Go 2x Doran's (if needed), Catalyst, RoA, then Frozen Heart or Spirit Visage. The %HP sustain from your passive becomes effective once you get some HP from Catalyst and you can start pushing/bullying hard if the enemy jungler isn't around. His roaming potential is insanely high, especially with Flash up, so going into full push lane and roam mode earlier than expected can be effective. In mid to late game teamfights it's often possible to keep your ultimate running for entire fights, protecting your team and zoning out any divers. Just build smart tank items sometime Locket, often FH, sometimes Thornmail, you know the drill. He's big weakness is relentless splitpushing as, although he can be impossible to kill 1v1, he wants to teamfight.