This is a way that I've been playing Maokai over the past few days. It's actually been working out pretty well for me. The only time that it hasn't is when my teammates were going suicidal on the enemy team. So far with this build i'm 3/1 (which I know isn't very much) and usually end every game with few kills, few deaths and several assists as a tank should. The main thing about this build is that I don't level sapling for the pure reason that if you do level it, you're basically saying you want to go damage and not tank/support. You're more likely to end games earlier if you build Maokai this way because you'll be supporting your team by slowing and snaring theirs.

You may or may not see my runes as a bit oddball compared to most tanking runes. My runes are this way because this is just my runes that I use for most tanks. You can feel free to experiment with the runes and stuff I just like these ones for my own personal reasons which I will explain.

Magic pen. marks. These help with your overall damage output considering that if you use this build you won't be doing much damage with sapling. It also helps farm slightly.

Health per level seals. Obvious reasons. More health = more survivability.

CDR glyphs. Obvious reasons again, using abilities more = more support for team.

Attack speed quints. Helps with farm.

The current items shown are just your basic ones for a game that ends earlier than say around 35 minutes. Obviously you would want to upgrade the two gold per 10 items into their upgrades so that way they're more helpful.

Heart of gold and Philosopher's stone. The gold per 10 on both of these items helps quite a bit since depending on who you're laning with/against you may not get a lot of creep kills because again, not upgrading sapling. As well as the future upgrades for these items will be very helpful later in the game.

Quicksilver sash. Very cheap item for how much MR you get from it. That and the cleanse ability it has will always be helpful in a pinch.

Warmog's. Obvious. More hp = more survivability.

Now for later items after these basic ones.

Depending on what's going on it team fights you can get any of these items.

Force of Nature. Lots of magic resist and hp regen. Good against all magic carries.

Aegis of the Legion. Decent amount of armor/MR for the cost. Also has a very helpful aura for your teammates. Makes you more supportive.

Spirit Visage. You would actually want to get this earlier if you want the extra hp gain from your passive.

You would also want to upgrade the Heart of Gold into a Raduin's Omen for the massive amount of armor it gives as well as CDR and hp regen. As well as upgrading the Philosopher's stone into Shurelya's reverie which has a little bit of hp and CDR. But the movement speed increase from the active makes you more supportive to either chase or run away.

My reasons for this skill sequence is as I said in the intro. Sapling = more damage. Twisted Advance and Arcane Smash = Better initiation and more support to help your team get kills.

Often times when I have a jungle on my team I try to take solo for the sole fact that you have one of the best ways to keep an enemy from getting away when your jungle tries to gank. You have Twisted advance which will keep an enemy still long enough that you can go around where they're possibly going to run to and then arcane smash them in the other direction. So basically he's a ridiculously good champion for solo and get your jungle fed up with some early champ kills.

I've also had a few instances where the enemy (whether solo or not) would stick around with low hp twisted advance and arcane smash + your ultimate can actually land you a few kills for yourself. Extra money is always good.

This is just my basic way of tanking with Maokai. It works very well and the extra gold from Heart of Gold and Philosopher's gives you the money income to help get items. If you feel that I should make changes send me a message and I might consider changing this. Feel free to experiment with runes and masteries and such. It's not like I own this build. ^.^