Breezy you better not be trolling me bout Nasus. buying him now (well hes so cheap)
I'm not even Joking
Tips on Nasus-
Have an MR page set up and an Armor page set up(That is, either MR quints or Armor quints)
Don't trade until you get Sheen
Don't spam E or W to harass unless you have your sheen as they use alotta mana
Always be wary of ganks. Expect to be ganked immediately at all times and this will help your laning.
Triforce is good, you can crit more than ADCs(With the exception of Cait and a charged up auto) with it and Q(I've done crits as high as 1600)
Farm as much as you can
Try to build Triforce first with a Glacial Shroud as a side item(And/or Spectres Cowl if the enemy is AP)
Merc Treads if they have heavy CC, Ninja Tabi otherwise
Spirit Visage should be the 2nd item you complete
Dead Mans Plate should be the 3rd
During the Mid/late game, either buy Warmogs for the 4k+ Health or Frozen Heart if they have heavy auto attackers
As always, be mindful of the opponent. For example Renektons and Rumbles can bully you levels 1-5, but once you get that Sheen you can efficiently trade with them. Sheen will also heal you about 80 health points on last hits(When you get Spirit Visage, which should be around level 9, you'll start healing for upwards of 200 health with each Q if it's been properly farmed), either way Sheen gives you a decent sustainability in lane as well as letting you trade efficiently(If your Q farm has been good, you can chunk your opponents of their health.)
Once you reach level 10-12, you'll be able to win any fight 1v1 and the opponent will have to gang up on you. If you reach level 16 and are decently farmed as well as completing a few items, even the whole enemy team will have trouble taking you down(Making you the perfect initiator/peeler).
As for your wither, that's a whole other minigame right there. Wither priority is as follows-
1.Enemy ADC that can't cleanse out of it immediately
2.Enemy Mid
3.Everyone else
During laning-
1.Use Wither if a gank is right there
2.Trade with the opponent if you have Sheen with Wither, you can usually get 1-2 Q hits before it runs out post level 5(It's easy to cause them to waste flash)
3.Always use wither during the beginning of a trade, not to chase. Since it lasts for 5 seconds and increases over time, not only will they not be able to trade as efficiently, but they'll be forced to flash if they're trying to run.
For his E-
1.E is only good for farming if you have a huge wave and you're not under tower
2.E lowers the enemies armor, so because of this it will cause your tower to hit minions alot harder(Thus bad for farming under tower)
3.Because of its property, the combo for attacking an opponent is E+Q. This will guarantee your Q will hit massively, and even though it's mana intensive, if the opponent doesn't have pots, 2 or 3 applications of this combo will guarantee your opponent leave the lane(Easy to do if the opponent is melee).
4.E is a great finishing move since its damage is frontloaded, many a time I've had an opponent flash with sub 200 health thinking they got away, but being able to E them and kill them is satisfying.
On his R-
1.It gives him a huge health boost
2.It increases your own base attack as long as you stand near enemies
3.It also does %damage to enemies, meaning that the longer they stand with you the faster they die
4.You can use it to avoid 'executions', IE Lux laser or Gangplank ulti, because of the health steroid
5.If an opponent has ignite, you'll still gain the full HP, another way to deny ignite killing you
Nasus is great when played properly. But at the same time he does have shortcomings, such as a dangerous early game and dependency on his Q stacking as well as items to round him out. He can't trade early against some characters that are aggressive and have front loaded damage(Irelia, Rumble, Renekton). For these cases its best to work on farming Sheen and then trading with them, they can't heal fast enough compared to Nasus to trade effectively.