Diana build

What do you guys think about ludens echo on Diana? I feel like it's a good item to help with mana, dmg, and cdr in early game. Cause I like to use her q to get a lot of farm when i'm up against ranged champs in mid (ex. neeko) and I like to use it for poke too. If you can, can you explain why ludens echo is not a good item on her or tell me what item is usually best for 1st item.