Other guides are good:
But their items didn't really make sense to me. Blink in and die? Aghanim's gives his ult great range plus a bunch of stats and a lower CD. Put your blink money into a faster Afghanims. Drum is a decent item, helps with move speed a lot but it's not as strong as Heaven's Halberd. 9dmg vs 45. Pick up a cheap vlads for more damage, leach, and armor if no one else has picked it up. Your a semi-carry, add crit. Last item isn't really that crucial. If you're focusing on ganks, and pushing, while occasionally clearing the jungle, very rarely will you get time to farm ancients.
If someone else grabs vlads, a Helm of the Dominator or Armlet is a substitute. Armlet is a very cost efficient item but it has drawbacks and I don't really see how you could run it without life leach. However that damage boost would help for the 4 second stun on your ult.
Soul ring helps with regen. Stats on Afghanim help with mana, can also tread switch for mana.