This is my first published build...
Hope it works for you all as well as it does for me.
The idea behind this build is keeping your fingers busy. I've always preferred to have some cool down but this build gets a little crazy with it...
Mid is my preferred lane so this guide is really speaking from that angle.
Items - The Balance of mana regen and ability power
I've been going doran's ring and meki pendant from the start with xerath. His early game relies on landing shots and having the mana to do so while still pushing/holding the farm with ease. Although ability power is always nice, xerath has nice AP to start with and as long as you can keep shooting, you will make up for that opportunity cost of buying mana regeneration rather than ability power early by just landing more shots on target more often.
BOTTOM LINE:Im a big fan of this mana regen mindset. It keeps you in the lane and in the fight without having to buy mana potions or waste a slot on clarity spell. This build focuses on sacrificing some ability power for mana regeneration
Morrello's Evil Tome Good overall item that contributes to the cooldown idea while at the same time adding nice ability power. Good item for almost any AP champion.
Deathfire grasp is only an item I have been going with more recently. I like its passive and like its ability to generate some cash as well as its decent ganking bonus from its active. The negative is it is expensive and doesn't have the high ability power for the high price. As I said before, it will make up for this deficit with Kage's lucky pick and this does make it less important to farm 100% of the time possible. In other words it still keeps the cash coming in when going after top and bottom lane ganks and buffs in the jungle.
BOTTOM LINE:Good overall AP item. I consider it an AP carry item. Really shines when you have the chance to grab it early. Although my item progression, shown above has this after Morrello's, I sometimes get it before, especially if your team is up. Its active is like a champion smite and is great for just chopping an enemy down in an instant when ganking. GRAB KAGES PICK ASAP! Dont be afraid to use the active EVERY time it is up. Cooldown is only 1 minute. NOTE: The active is 30% of the target champions CURRENT health so use it early
From here on out its just Ability power and effectiveness. Don't think I need to sell why Rabadon's Cap and void staff are necessities for ANY AP champ.
Adjust final item to what you see fit. Abyssal Scepter is just the default I like to grab. Just makes you an overall more effective AP punching champion. NEGATIVE about it...the unique passive is an aura therefore the target champions need to be near enough to you for its effect to reach them...the issue with this is Xerath's extreme range. I believe when you are firing at your most extreme ranges, the aura falls short and the targets are ineffective although I have not 100% tested this. If someone could comment and fill me in on the dilemma, please do, I'm very curious.
Xerath is simply a great farmer...this build just makes him better with all the cool downs and mana regeneration. Xerath can 2 shot minions even if you are a bit behind the leveling curve. He can keep other champions easily away if you are dominating the creeps and even if your not, you can still easily land shots to farm creep and land champion damage.
Set an attitude early. With this early mana regeneration, keep the shots firing at your lane opponent often and keep the physiological battle high. All this button mashing means you can protect your minions and really keep other champs off them. No champion currently released can deny you your farming rights with xerath's range and ability to pop shots off with easy from afar often.
Also keep in mind...Try to line the farm up when taking shots at the opposing champion, even if you miss your skill shot on the champion, you still get farm damage and/or money.
Pretty straight forward rune build. Like a little mana regeneration and this is just to help your early game even more on the mana management front.
I like the Quintessences of pure ability power rather than the AP per level. It helps in the early game to really get you rolling with xerath.
Flash:Good for offense as well as defense. Nice for securing that kill after the target has flashed. Saving your w for after your flash is an almost guaranteed e,r,q combo hit. His range is just massive and putting a flash in there too puts you shooting way past the targets guess.
Ignite:Good for securing that first kill mid lane but thats about it. Surge is a smarter option but I have not grown accustomed to it yet. I am an ignite NOOOOOOB!
This build has served me well and is alot of fun. You always have something off cool down and therefore something to do. This build along, with my playstyle, is focused on early domination and kills. This is key with any AP champion and xerath in my opinion is the best!