I am having mix success with maokai and trying to do some builds. Anyway, wouldnt archangel be guild on maokai? Personally, I am a huge ability spammer. Mainly using his e and q to wipe out creeps. Then using his W to gank enemy and hold them down then unleashing hell. He gains mana regain and 2 percent of his mana goes to his ap. So, if getting it early as possible and going into late game. Wouldn't this be a good item? I know most maokai are tanks, but as a caster he pretty decent.

Because he has to get up close he needs health and resistances. His passive scales off health too. His Ult also complements building health on him by Reducing 20% of non-tower damage taken when in the circle.
I wouldn't buy something like Archangels on him.
If you wanted to go AP build, ROA would be the first one that comes to my mind. Builds from catalyst so you won't have mana problems. If you want to push waves and just spam spam spam then just go B after using all your mana. Or get blue buff.
In no real order.. Roa, Rylai's, deathcap, boots, abyssal scepter and zonya's. I think that'd be a good AP Maokai.

That's just how I would do it I think, but There are better tanky AP's.

Standard Maokai build is Catalyst > Mercury's Treads > upgrade to RoA > tank items depending on enemy team.
There isn't really much point in a true AP Maokai - his damage drops off fast and he'll die before he does it half the time. You only build to improve his early-game burst, and treat him as a tank with solid damage after that.

Mao doesn't have a dire need of the mana from an AA staff. Additionally, he's melee range so you don't want to build glass cannon items on him. Better to go with tanky AP items instead if you really want to do that.

A tanky CDR build with a splash of AP is far more effective than a full on AP Mao anyway.