I choose this order because if you are ganking right off the bat I find that popping him into the air lets you and your ally get the most hits in. After that initial fight though I find that I typically am not doing anything with Xin till lvl 3 except maybe farming. After level three though it's on. q-w-e wait for the pop up then r if you have it.

This is my item build I find works best when the other team is made of squishies. You'll find that you sneeze and by the time you open your eyes they've eaten 9 hits and they are dead.

Realisticly if the opposing team is tank substitute a Madred's for your second phantom dancers and a Last Whisper for your first Blood Thirster.

If you find that you got ganked a few times early game after your first phantom dancers dont be afraid to settle, Beserker greaves, Executioner's callings and Bilge water cutlass are acceptable to get you stats but don't plan on keeping them. You get into a hole you fight your way back out of it and try to get back on course. Compirmise but know when to. You dont want to end up with 3 or 4 shoddy items in late game that you have to sell and replace because you lose gold and its irritating.

Pro
Hits hard and fast
Passive life regain

Cons
I can not stress enough how squishy xin is if hes not hitting someone. I have seen myself eat Lux's stun and be dead before it wears off where as if you are hitting on something between your natural life gain and blood thirsters you never die. With Fullbloodthirster stacks on this build you can take on any other champs in the game 1 vs 2 AS LONG AS THEY DONT HAVE CC. CC kills xins! Avoid it. Late game its less of an issue but early game if you find ur laning against heavy CC teams dont be afraid to ask to switch.