If we put on a scale, most of the dmg come from her abilities (like 45% of the times you will be spaming), so in the end you would be getting a lot of issues with your CDR and MP so is your best item so farm, and later get .
Usually you will be getting as your boots, but if u dealing with so much cc or bursted... think on getting or .
Now here is when thinks get tricky.... Right now you will have 20% CDR with a nice chunk of AD. Your goal should be getting your CDR cap, and my recomendations are the items showed up.
Other items that can work well with xaryah:
while your W is on, give 2 stacks per AA, so its a way to shred some armor.
Movility is always good to make some distance with your enemy, since xarya have the combat ability to make some really nice plays (Ult + E, almost always a good root)