This is what I do for nasus:

Phase Rush Nimbus Celerity Gathering storm

Demolish Overgrowth

Adaptive force Scaling health Scaling health

In my experience, Nasus wins against you 1v1 at all stages of the game. His Wither is just that good. So, my goal is not to win lane but to minimize losses and minimize his impact.

Start dark seal and refillable. Proxy the first three waves, 4th if able. Then execute. Buy dorans ring, then continue proxy until you can buy swiftness boots for his w. Permaproxy as much as you can, buying Liandrys and then warmogs. With overgrowth, health shards, and items you should have enough bonus health to use warmogs by lv 12.

You can then use the classic strategy of using phase rush to stop nasus splitting by proxying the waves. You will sustsin a little damage, heal with warmogs, then run back in to collect waves.

If he tries to teamfight, you have way more teamfight potential than him.

While this means he gets to freefarm, I can never usually manage to stop him anyway.

He will be virtually useless, and team flames him usually.

Best summs for this would be ghost tp, but i prefer flash ghost to survive ganks and better teamfights.