Not Updated For Current Season
The masteries shown here are not yet updated for the current season, the guide author needs to set up the new masteries. As such, they will be different than the masteries you see in-game.
To start out, the items I have listed are the final items, not the order you get them. I usually start out with an amplifying tome and a health pot. Usually get the Giant's Belt next, then go for Rylai's. After that I can usually stay out until I get enough for the fiendish codex. Finish off the Nashor's Tooth as quickly as possible (usually around level 8 or 9) After that, just whatever you can afford. I usually get Zhonya's Ring next, while it's still semi early (level 14) Then finish off the items. For skills, go for Ice Blast first for harassing. Get consume next so you don't have to recall as much. Try not to leave until level 5 at least. Masteries are open. I usually go 0-9-21 but that's just me. Summoner spells go for teleport because flash and ghost are kind of useless, because blood boil makes you fast enough to out run most champs, and clarity should be self-explanatory. Play it cautious until you have your ult and 80+ ability power. You're gonna have a LOT of assists. Pro Nunu's can be the difference between winning and losing, especially if you're the only tank. That's why I include Thornmail in my build for a little more survivability.