Hello There
This is my first build, I hope it works out for you guys and any advice would be wonderful. This, as I've hoped you've noticed, is an AD Nasus build. However, it does end up quite tanky in the end. Anyway, thanks for reading and do enjoy!
Oh and thanks to SalazaShi for telling me to do this!

Pros
-Can stay in lane a very long time
-Also good support
-Main source of damage is low mana/cooldown
-Doesn't need early game kills that bad
-Free lifesteal! :D
Cons
-Very late game
-Slightly squishy early game
-Doesn;t do too much damage early game

Honestly, it depends how you play the game. If you like to be more defensive, 9/21/0 would be better for you, this gives you an easier early game because you are much more tanky, but with that you might as well go as tank Nasus. If you are like me, you can go a bit more hybrid and be 14/15/0. This is for AD. Another option is to go something like 10/10/10, but this is also a tank path.

Core Items
Situational Items:- Well, if they have a lot of AP then get these.- Only get this if you are really fed. The Guardian angel is alot safer and is probably what you want if youre abou 6/5/13 in KD- This is for if you think to yourself, 'Screw Spirit Fire! I want the health to DROP.'

The skill sequence listed is pretty much what you want. You can switch up between wither and Spirit Fire, depending if you are really going hardcore on the auto attacks. According to their team, like if they have Rammus and Malph, then go for your Wither. This he;ps you when you need to keep them out of the fight, while your team goes for their carries. This also helps in the act of slowignt hose carries. But, if their temais full of squishy people, its very usefull to keep the Spirit Fire in the middle of the fight dealing some AoE Damage over time. Your Siphoning Strike is essential to AD Nasus.

Okay.- I prefer flash overbut thats just me. If you've got flash, you can simply be away, but with ghost you can still get cc'd while you're running.

- You can use this, but you probably will have to use it with ghost, mostly because if they are getting away you can catch up to them easier and stay up there also, to secure the kill you must still attack. I like ignite better for the bonus AP after the use, giving your Spirit fire a nice little boost for its damage without buying any AP.

This is what everyone thinks: "Oh a Nasus! Tank! Yay!"
Well this isn't the case. if your AD carry is laning top with you, and dies, saying 'Stupid Nasus doesn't know how to be a tank' calmly explain your situation to them, saying you are AD. Do not rage at them. This will result in a bad game and no-one will have fun. This goes as is in team fights. You are still sort of a tank! Act as one in team fights if your team does not have a second. Your Yi is a better carry than you, so take your still lingering role of a tank into action. This doesn't mean you have to change your items, just check the stats!

Alright, thats all for now. Remember to keep your cool, talk back to trolls and get some good IP. I hope this was helpful to you people and may add more chapters in the future. Sorry if i wasn't clear on something, but hey, that what the comments are for. Also, not all builds are for everyone so if this doesn't work for you I understand.
Keep pwnin dem noobs,
Raazac Shad0w