Just stack. Jungle Monsters gives you 12 stacks. Your goal is to reach 150 stacks before or at 10 minutes. After then 100 stacks per 5 minutes. Cinderhulk will help you with the health and you will heal with smite and your Q. However, watch out for the chickens. Make sure you also stack the dragons instead of smiting if possible.

When you have your Trinity Force, you get 40% cooldown reduction. With that, it's really easy to stack and with a maxed out Q, you can use it every 4 seconds. Getting 100 stacks per 5 minutes after you get Trinity Force and some other items such as Iceborn Gauntlet will be a breeze. Phase rush is important when playing Nasus. When ganking, if you hit 3 skill shots or auto attacks, you gain a lot of speed. Make sure you stay ahead of your enemy using this and use your W to slow them down as well. If you can, stack the enemies because they give you 16 stacks!

You should have around 400 to 600 stacks in ~30 minutes depending on how much you tax your lanes. If you have over 400 stacks and have your second last item, join team fights and help your team with pushing a lane. With 400+ stacks, you can melt away towers, dragons, and inhibs.

*100% per 4 games :)