Hello, this is my build of Maokai as tank. this works best for me, so i hope it works for you as well.

and im not good writing a guide, please bare with me.

Pros:
Can take some damage
Has throwing bombs
Really great initiator
Amazing team support

Cons
Mana dependent
Not the greatest champ for a solo lane

The reason i go for utality is that hes a very slow champion and he needs it.
and he will be tough enough with this build :)

Remember that the items i have listet is the first items i recommend, the rest is up to you, since i cant see the team you are going up against.

but some good items would be

Thornmail
Rylai's Scepter
Guardian Angel
Abyssal Scepter