Great alistar build!!! i couldnt think of anything better +1

Updated to a better item flow for me. This is how I have been building him for a while now. Responses are welcome, thanks.

Okay.
Okay.

Warmogs first item? Usually never a good idea on tanks. Gives you lots of health but no armour or magic resist. Expensive item too. While yes tanks need health early, there are better alternatives, like heart of gold into randuins, sunfires for early armour or Aegis for all round use.

Ruby crystal as your first item is a general no no. You'd be better off starting with a regrowth pendent and a pot (mana or health, your choice) to avoid early harass. Ruby crystal = 180 health. Health pot = 200 health.

Boots of mobility is fine for a support Alister, especially a roaming one heading about to gank on lanes.

My next major issue with the guide is you only reccommend one item that gives mana and no items that provide mana regen. You're going to be mana starved for the longest time, especially if you're going to be spamming heal a lot to fill the support roll.

The 'support' items you have picked are very specific case. For example, Frozen Heart is strongest against an AD carry (likewise with thornmail but that's not support), and Abyssal is best if your team has a strong caster presence. You haven't listed any general support items like Soul Shroud, Shurelya's, Aegis, for cooldown reduction or buffing your allies.

This build is incredibly light on magic resist. You probably won't break 100. Overall, I'll say now, and it'll probably seem mean but that's not what I'm aiming for;
The only thing about this build that is support is maxing out your heal first.
Any 'support' items you do have are aggressive, as in, they weaken your enemies, not strengthen your allies.

I use to use Boots of Mobility in my Tank/Support Alistar as well. I find it better to use Mercury Treads due to the tenacity. Plus you get more magic resist. If your looking for speed Boots of Swiftness would be a better choice. I like the concept of Abyssyal sceptar. But it doesn't give as much magic resist as a force of nature. :P Plus a FoN gives really good health regen. Good build other wise.