OK, so I made this build forever ago, and there have been quite some changes in the game. Thanks for all the comments and upvotes, and sorry I haven't really been back on here so much.
Currently I switched to flash and ignite on him, and I start off the game with a mana crystal and one of each pot.
I rush a RoA still, then get boots. I'm not very consistent with boots as I base it off of what I'm against. So make a decision if you want movement speed, cooldown, or resistances.
After that if I need to be the tank for the game I get either a Rylai's or I get BV and Omen. If not I will rush a Rabadon's and then get a Rylai's. The items up top should work for most games, but this build is more of guidelines than something set in stone. The idea is to go as much AP as possible but, as Alistar you will be expected to take some damage. These items are what I strive for most games, order is only based on what I need for specific teams.