I've been playing Cleste a lot and you really want to have massive CP on her. 3 defensive items will make her damage terrible, and she's still fairly squishy meaning you're basically useless with this build. I can think of some situations where you might want 2 defensive items, say if you're facing Ringo and Taka at the same time, and maybe nobody on your team has built Crucible or Fountain of Renewal, but for most cases 1 defensive item (other than boots) is good enough. In the end, the defensive items should only help you survive long enough to dish out your max damage, enemy should by fried by then if you have enough CP and have done it right.

Why would you build a tank Celeste? She's more of an ADC hero.I would only build one defensive item. And why no clockwork? You can spam your abilities with a clockwork.