NASUS

Nasus is a weak early game champion with scaling damage. He gets 3 ad with his q for every stack he gains. He gains a huge powerspike when he hits level 6 and then another when he finishes his cdr items.

Sorcery

Phase Rush - Phase rush is very strong on nasus since you are already going to use w to slow and e to damage the area they are walking, then you just need to hit one q and you can stick to them every time you ult.

Nimbus Cloak - Nimbus cloak is an insanely strong rune on nasus because he will be able to stick to an enemy during his strongest time, his ult.

Celerity - This rune is also there for your ultimate because you will be able to stick to your enemy with the extra movement speed.

Gathering Storm - Gathering storm works well with nasus because he is a scaling champ with his q, so he will scale even better with this rune.

Inspiration

Biscuit Delivery - Nasus does not have the strongest laning phase so have the cookies will help you to sustain in lane and survive against agressive laners like darius.

Approach Velocity - Again, this rune works well when you plan on using your ultimate, because your Wither will slow them slowing them and giving you movement speed.

Trinity Force - This a great item on nasus because it ticks all the boxed cdr,ad,attack speed, mana and movement speed.

Boots of Speed - I left this on the default boots because it is circumstantial on what the enemy laner and his/her team consists of.

Frozen Heart - This item slows enemy's like tryndamere's attack speed and also give a lot of mana and cdr essential things for nasus early and late.

Iceborn Gauntlet - This item is great for nasus because it gives mana and cdr just like frozen heart, but it slows the enemies when you auto them after an ability, this works with your q, this will almost ensure they can not get away.

Dead Man's Plate - This item also works very well with your q because you will then deal even more damage, with the runes you will also move faster giving more stacks to the item faster.

Adaptive Helm - This item is great vs champions like Teemo who deals frequent weak ap attacks. It also gives cdr so you can stack more.

You will almost always max your q Siphoning Strike with the new update in patch 9.1 you get 12 stacks from cannons and champions, making this ability even stronger to pick up from the start.
In the few situations you won't like when you have to play EXTREMELY safe, you can max Wither.

Unless you are going ap do not max e Spirit Fire.

And obviously take R Fury of the Sands as soon as it is up.

Flash - I would say flash is a must for any champ, except some special cases like shaco. It allows you to get into the backline and q the adc, to get out with a sliver of health and to get to lane faster >:).

Teleport - I recommend this summoner spell because it gives you a way to split push but still be a threat in team fights.

PRO'S

1. You scale endlessly.
2. You get to farm safely with your Q.
3. You can pressure other lanes very hard because of your strong split push
4. He is an easy champion to learn.

CON'S

1. He is very weak early game.
2. He does not have a lot of cc, only his slow Wither.

In lane

1. Just try to lasthit as many minions as you can with your q, cannons give double stacks.
2. Do not sacrifice minions to stack on other, or risk losing one because of Q cd.
3. Do not use your e for cs'ing unless it is neccesary, since it pushes the wave and costs a lot of mana.

Under Tower

1. Your q makes lasthitting fairly easy under tower.
2. If you get dove or harassed use your slow Wither to make them extra tower shots.

Teamfighting is not the easiest thing for nasus vs poke teams like ez and zoe, so try to force an engage so they can not get as much free damage onto you. You should be the one to frontline and get the carries or zone them. He can not survive vs a whole team though, you will need help from your team to stay alive or atleast win the fight.

Stacks

Every creep gives 3 stacks and every cannon gives 6. This is essential to being effective late game.

GOLD

Creeps give gold, this is obviously crucial to achieve success, another reason to split with nasus.