Build Guide by theFredy

This build is assuming you have more than one person on the opposite team with ability power, if its mostly melee, you'd get ninja tabi instead of merc treads, after your 2 sunfires you'd get a R.omen, a thornmail or another sunfire cape depending on if they have a lot of damage output or more survivabiliy (lots of dmg = thornmail, survivability = sunfire cape). I'd also like to add that before you get the last iteam, I usually switch merc treads out for Movement speed 3 boots.
you're probably asking me why did I include the zhonya's ring. First of all it gives all of your abilities a boost, and if you bind the ring in it's a pretty useful tanking weapon, assuming you've already tossed and ulti'd into a group, it might give your team a couple of seconds to catch up to you or finish others off in the confusion.

Early game: not too offensive here, you're better off with a ranged character that isn't afraid to shoot* try not to go back until you have enough for Phil.stone and first boots. Don't be afraid to bandage wrap your opponent if they get too close to your turret, its happened to me countless of times and usually ended up in a kill.
Mid game: look for opportunities, make sure your teamates have your back, an ulti without your team is a wasted ulti, the best part about it is that you set multiple opponents up for a kill for your teamates. Also don't be afraid to ulti if you're outnumbered defending your turret, you can usually catch a kill or 2 because most people don't think that amumu is a threat and try to take the tower out with you right next to it.
Late game: you should be a pretty solid tank at this point, make sure your party has their ulti's up before you engage and do your best to kill the other team, make sure you're constantly going for the squishiest target and use your bandage wrap whenever its up, it can change the pace of a fight if the enemy is stunned even if its only briefly.