This build good for pushing and best choice in team fight.
Hmm sounds like good.... I created this build after i did quadra kill with it.
Focused for hp per sec damage and damage over time skills.
If you boring AD Nasus's build and want to have a fun this is your build.
Hard to kill Nasus with this guide.Try and test it.
Have fun.

Pros

Easy farming
Great pushing
Hard to kill in teamfight
Can be tank
Can start gank


Cons

Mana problem in early game
Little useless ulti without teamfight
Item dependant

Armour and magic resist are makes you harder in team fight.

Ability power and Magic Pen are boost your spell damage.

Both are very important.

Let start with Boots and 3 Health Potion

First Catalyst the Protector because hp and mana reg.You can hold on your lane more time with this item.

Mercury's Treads should be finished it makes you Tenacity

Liandry's Torment is next.This item place dot on your enemies (damage over time) every time if you dealing spell damage.

Liandry's Torment+ Fury of the Sands is a great combo.

I go with 2x Rabadon's Deathcap

and Enchantment:Distortion for damage boost and Flash and Teleport cooldown reduction.

Rod of Ages

and

Warmog's Armor
are next to make you even tankier.

Play Video

Soul Eater
(Innate): Nasus drains his foe's spiritual energy, giving him a natural 14 / 17 / 20% lifesteal.

Soul Eater this is will keep longer in lane and give for you more agressive gameplay.

Quickly hp reg if you have low hp.

Siphoning Strike
(Active): Nasus next attack within 10 seconds will deal additional damage. Siphoning Strike permanently gains 3 stacked damage whenever it kills an enemy champion, minion or neutral monster.
Cost: 20 / 25 / 30 / 35 / 40 mana
Cooldown: 8 / 7 / 6 / 5 / 4 seconds
Physical Damage: 30 / 50 / 70 / 90 / 110 (+1.0 per attack damage) (+3 per enemy killed by Siphoning Strike)

Siphoning Strike good with Soul Eater for more hp reg,and good for last hit an enemies and mobs.

Wither
(Active): Nasus ages his target, slowing their movement and attack speed by 35%. Additionally, they are reduced further to reach an extra slow at the end of 5 seconds. If the duration of the slow is reduced, the extra slow will be applied faster for it to reach its maximum at the end of the duration.
Cost: 80 mana
Range: 700
Extra Slow: 12 / 24 / 36 / 48 / 60%
Cooldown: 15 / 14 / 13 / 12 / 11 seconds

Hard to run away from me with this spell. Use cleverly important.



Spirit Fire
(Active): Nasus unleashes a spirit flame at a location for 5 seconds. Enemies caught in the area are dealt a burst of magic damage. Additionally, enemies in the area are dealt magic damage each second and have their armor reduced while on there and for 1 extra second.
Cooldown: 12 seconds
Range to Center of AoE: 650
Radius of AoE: 400
Cost: 70 / 85 / 100 / 115 / 130 mana
Initial Magic Damage: 55 / 95 / 135 / 175 / 215 (+0.6 per ability power)
Magic Damage Per Second: 11 / 19 / 27 / 35 / 43 (+0.12 per ability power)
Total Magic Damage: 110 / 190 / 270 / 350 / 430 (+1.2 per ability power)
Armor Reduction: 20 / 25 / 30 / 35 / 40

Spirit Fire is my main skill and useful for farming and team fight.



Fury of the Sands
(Active): Nasus becomes empowered in the sandstorm for 15 seconds, gaining extra health. While the storm rages, he drains a percentage of nearby enemies max health each second (max of 240 magic damage per second per enemy) and converts 6.375% of the damage done into bonus attack damage for himself until the sandstorm wears off.
Cost: 150 mana
Cooldown: 120 seconds
Radius of AoE: 350
Health Gained: 300 / 450 / 600
Max Health to Magic Damage Ratio Per Second: 3 / 4 / 5% (+0.01 per ability power)
Total Max Health to Magic Damage Ratio: 45 / 60 / 75% (+0.15 per ability power)
Total Magic Damage Possible (to a single enemy): 3600
Total Bonus Attack Damage Possible (from a single enemy): 229.5

Fury of the Sands + Liandry's Torment nice combo in all of game.
Just use Fury of the Sands versus more then one enemy

Try it and have fun. :)