I don't know what elo you are, but, based on your large amount of kills/assists and the fact that you have a tiamat, you're probably pretty low. I don't say this to insult you, I say this so that you understand that while this build may work for you at your current level you won't be able to get away with wasting gold on subpar items once you get good.

I would recommend getting a trinity force first. This will give you enough dmg to carry in team fights. Then getting survivability based on the enemy team's composition. Are you getting raped by magic or physical dmg? If physical or both, get a sunfire cape. The health and dmg will assist you against magic dmg enemies as well. If magic, you have a couple options: Warmogs, Hextech Drinker, Guardian Angel. I haven't figured out which one of these works best, but they are all solid items. After that, you just build what you need. Dmg or Survivability. Are you getting focused down immediately in team fights -> Survivaibility. Are they ignoring you and killing you last -> dmg.