What should i build on 
Top lane/Jg?....Coz he is a good alternative to 
& 
who are banned mostly in drafts...So is Nasus Ap Tank or Ad Tank? And what should the build order be like... Mobafire guides didnt work well for me... So it would be great to know current pattern of Nasus if it is played by anyone in patch 5.21.....And also when should i pick in Drafts??...... Thanks in Advance guyz
nasus starts of by building cdr and tanky NEVER NEVER NEVER NEVER NEVER put it in your dam head to start of building dmg if ur seriousely playing
countless times i see people build 
or 
first item than whining that they lose lane
your supose to rush that 40% cd 
so you can q minions faster and get stacks faster so u can get stacks for a shit ton of dmg
possibly 1 hit the adc
while only building tank items
<--- items like those ;P
dont get me wrong if u want triforce u can get it just dont go out rushing a triforce without having cdr/armor/mr and than proceed to get ur ass kicked cause ur a squeeshy nassus
Nasus is a somewhat weak early, good midgame, average lategame (insanely good in 1v1 but very lacking in teamfights) champion.
As Nasus, your main source of damage is your Q that, you probably know, gets stronger with how much creeps you last hit with it. So during the early game, you are going to try to farm it as much as possible while withstanding enemy's harass and you can't really trade back.
So that makes you want to pick up resistances, and cooldown reduction (cdr). Cdr to have Q faster and farm it quicker, resistances because they synergize with the lifesteal from your passive (if you take less damage, the lifesteal you get back is more efficient).
Basically, the typical build is 
. You can obviously change some items and adapt your buildpath, but typically you rush against AD and against AP.
Once you got 400ish stacks (should be done by the 20th minute mark), you can start playing very agressive because you outduel pretty much anyone.
CDR and Spirit Visage are a must. And it's best to put a Sheen related item somewhere in your kit, don't do Lichbane tho.
Other than that, build tank, and you must avoid AoE damage items like Hydra or Sunfire. The only exception would probably be Iceborn Gauntlet because it's quite handy for him despite having an AoE damage.
A real pro nasus builds Trinity force first for deleting squishes early, getting kills, the mobility and mana, with an early sheen.
Building defensive early can be insanely powerful but i've found a way to get the best of both worlds.
Since nasus doesn't really need damage you shouldn't be building it in runes.
For red get full non scaling armour, for yellows get scaling armour, for quints get non scaling armour, for blues get scaling cooldown reduction.
Get the 5% cdr (45%) mastery and stormraiders and then go fully into the defensive tree (with the 5% bonus armour/MR)
For build start with three 
as they sell for 105 gold you aren't wasting much money, since nasus has high base regen its really strong and one builds into an item later saving your money, so make sure you keep one, full build is this.
or 
(dont complete) 
or
End with 
especially if you got merc
