Im a rank 7 Nasus and these runes and items are the best in my opinion and i mostly use these because they give a balance of dmg and health with the addition of amour and magic resist. (if you see another guide exactly like this, i accidentally posted it without logging in).

Note for Crit Build: You can have more fun if you bring dark harvest.

Pros: Nasus if played correctly can be a hyper carry, which for solo queue from bronze to gold, makes him very useful.

Cons: Nasus is very weak early game which makes it easier for the other laner to take advantage of creating a problem for Nasus. (you can fix this by playing safe, you can win lane most of the time because you will slowly overpower the other laner).

Sitting under tower and farming is the best way to get stacks and overpower the enemy.
Times for stacks:
10 minutes: 150 - 200
15 minutes: 300 - 350
20 minutes: 400 - 500
(note: having the most stacks doesn't mean you will win)
You should have kills in between stacking if not try and get a few and at about 350 stacks go help your team.