I go with Exhaust because it is outstanding against and AD champs and it will slow an enemy long enough for you to kill them

I got with Ignite just for the fact that when you take top and its your team verse the enemy it is just that much more damage going out

I think a good spell to go with instead of Ignite would be ghost just to make you that much faster to catch those pesky runners

I always get the berserkers-greaves with the dagger to get the attack speed and movement boost. Next I get the phantom-dancer. My goal is to get Xin's attack speed up as fast as I can. You can go with the black-cleaver or the the-lightbringer depending on how many tanks or stealthed units the other team has. Next I go with the infinity-edge because it just makes your damage outstanding. Now for lifesteal I have been going with sanguine-blade because it builds damage with the more hits you make and in 3 seconds in combat you are doing max damage and allowing yourself to exit combat with just about full health. For the last item most of the games I play with this build don't usually last long enough to get the Thorn mail but since Dominion is mostly AD champs never hurts to have some armor, or you could go with Warmogs with the amount of health you get from it....... makes you damn near impossible to kill

Pros
Strong against almost every champ
I have killed whole teams in seconds
run speed boosts along with items allow for getting enemy controlled turrets fast
people will go out of their way to avoid you
Cons
weak against Jax
weak until your second attack speed item is bought
can't think of any other weaknesses

I am currently not straight attack speed but i am working on it I only need 2 more marks and 2 Qs. Every time I get another attack speed rune I notice how much easier it is to kill everyone. So I am building towards it. Some guides say you need armorpen. but in dominion everyone starts out with 15% so I don't really feel like it is worth it, besides more attack speed equals more heals due to your passive.

Going with this mastery set up gives you a ton of offensive ability. Some people think it is better to go down the utility tree but I disagree. Think about it going down just for the increased gold? Forget that or even the increased Exp.... it is not worth leveling 4 seconds faster than anyone else. Instead go with increased MR armor and dodge you will last a while longer Utility tree is completely worthless for Xin in Dominion unless you go all the way do it but then you should just be shot for being stupid.