Hi all,
This is my first item build on mobafire, hope you find this useful and please send me feedback.

Lifesteal items
I like the essence reaver on kalista, because it makes you able to secure your farm with your E, without getting low on mana.
The bloodthirster gives AND tons of damage AND tons of lifesteal, good item if you are not low on mana.
The blade of the ruined king is definitely a good item on kalista, however using your passive gets much harder, since you have to click faster to actually leap. Furthermore, the use of your passive makes you attack less, such as the catching of draven's axes. In short: an item which requires a high skilled player

Defensive items

Guardian angel is my number one defensive item, because it is good when you are ahead as well as when you are behind.
Build Banshees when the enemy has a high magic damage output and/or a lot of ranged cc such as blitz hooks, thresh grabs, leo ult.
Build this when the enemy has a high physical damage output.

Offensive items

build mercurial scimitar when you want more damage but the enemy team has a lot of cc.
Build youmuu's for chasing, escaping and armor pen/cdr