I use this buid like the offtanky buid, but the difference is the AP instead of AD. This Alistar is able to survive a big fight while making really high amount of damage with his abilities and stun most of the enemy team to help your team to catch up with them.

I use this rune buid to have big AP at first levels (really great for alistar's heal), the mana regen and cooldown are the best late game because you can cast more abilities to make your targets' life even harder.

At first you can choose from 2 type of build. I found it better if you start with a Boots of Mobility and hp pots, but it's good too to start with a Doran's Ring. Doran's Ring is also good to stay longer in lane because of the mana regen and AP for heal. Banshee's Veil and Rod of Ages are good items to get HP, mana and durability and Rod of Ages give AP too.

try to keep your opponents away from your minions (easy if they are melee champs)it will be big (level and money) disadvantage for them. If you can get a little AP and you updated your Q your farm will be really easy just go between the caster and melee minions and push Q thats all.