"Beneath my warm exterior…permafrost." - Lich
Level 1 - Frost Blast / Sacrifice
Level 2 - Sacrifice / Frost Blast
Level 3 - Frost Blast
Level 4 - Sacrifice
Level 5 - Frost Blast
Level 6 - Chain Frost
Level 7 - Frost Blast
Level 8 - Sacrifice
Level 9 - Sacrifice
Level 10 - Ice Armor
Level 11 - Chain Frost
Level 12 - Ice Armor
Level 13 - Ice Armor
Level 14 - Ice Armor
Level 15 - Stats
Level 16 - Chain Frost
Level 17+ - Stats
This is a build I use all the time. I would get Sacrifice first and use it on a range creep so you can right away gain the early experience advantage. Sometimes you might not want to take it if you are guarding a rune or level 1 gank or level 1 rosh. You want to max Frost Blast fast as you can, because it's your main nuke and you want it to do much damage as it can. You pick up the ultimate skill Chain Frost on level 6 because you want to be team fight ready and it's an awesome spell. I prefer to get Ice Armor later because it doesn't really offer much early game unless you are getting harassed a lot then maybe a point of Ice Armor is good. I still like to get it later and put more points into Sacrifice to get more mana return from creeps, and it gives you more lane staying power. Remember to use Sacrifice on cool down and make sure you don't have a full mana pool all the time. You should be using Frost Blast then using Sacrifice so you can continually nuke heroes. Also remember once you get Ice armor don't forget to use it on yourself and your allies.
Lich is a support hero so please buy a Courier or Wards. If you don't pick up any one of those two you are bad.
You don't ever need to pick up Clarity because you will be using Sacrifice to gain mana back.
The Iron Branches are nice to have since it's cheap and gives you stats. It's going to be used later to make a Magic Wand.
Tangos and Salves are must have since you need that health regeneration.
I like to pick up Boots of Speed as fast I can, so you can get the better movement speed (very helpful to gank).
I also like to pick up a Magic Wand since the charges can save your life early on and it replenishes your mana, so more staying power in team fights.
I would only pick up Bracers if you are having a tough time surviving or just want more survivability.
Whenever you can, try to get a Flying Courier, it can only help your team and your carry(ies) so they don't have to go to the fountain or secret shop to buy items.
Aghanim's Scepter and Mekansm are the best items on Lich and should be picked up fast as you can.
Aghanim's Scepter upgrades Lich's ultimate skill for more damage which is amazing for him.
Mekansm adds that healing and plus armour and passively adds health regeneration, a great item for pushing towers and to keep your team alive.
Pipe of Insight is another great support item to get since it reduces magic damage done to you and blocks magic damage for your team. This might be better to get instead of Mekansm if you face a magic nuke heavy lineup. It doesn't hurt to have both
Drums of Endurance is a great pick up and an upgrade to the Bracer. It has decent stats, and it give you a minor movement and attack speed aura which is why it's such a great support item. It has only 4 charges to boost the aura effect by 5%, but the recipe can be brought over and over again to refill the charges.
For upgraded boots, I would pick up Arcane Boots since you are playing the support role and is very helpful if you have a low mana strength hero like Sand King or Tiny. If you don't have mana heavy team or anyone that needs it then you don't really need Arcane Boots for yourself so feel free to pick up a Phase Boots instead.
Force Staff is a great pick up for your team and yourself. If you ever are facing pesky heroes like Naix or Riki this is a great item to get out of harms way and escape their gank attempts. I like this on Lich better then blink because you can use this even if you are being attacked, and since Lich is not a great initiator this item suit him better and it has stats unlike the blink dagger. You can use this as a positioning tool and to get your allies out of harms way, especially when they caught in a stun. A great overall support item to get and a very fun item to use.
Scythe of Vyse is awesome luxury item because it adds a disable for Lich and he becomes that much more powerful. Not to mention the added mana regeneration and stats.
Shiva's Guard is a really good pick up because it adds more AOE damage, gives you armor, and AOE slow as well. Pretty good damage reducer for the enemy carry hero, with it's minus attack speed aura.
Eul's Scepter of Divinity is another situational item and useful to prevent focus fire on Lich by cycloning himself, also a good crowd control on an enemy hero.
Boots of Travel is nice to get since it adds mobility for Lich and you can move across the map much faster with this item.
Edited by Fayth, 16 August 2012 - 11:04 PM.
Updated. Added Force staff.