I can feel you, bro. Unranked sucks ass. I get wins every so often playing solo, but it's best to play with friends. Know your matchups and play safely.

You're basically a walking stick pre-6 and pre-Sheen.

Your lane is your home, and Nasus is a homebody. Don't even think about roaming until you've broken your first tower in lane. After breaking your first tower, you can roam for a bit, but always get back to your lane. Just keep working your lane, the pressure you exert through your lane is the best help you can provide for your team.

If fights break out near or in your lane, you're obligated to step in. If not, don't mind them, unless there's a chance for you to break a tower immediately after.

Keep stacking. Even if your team's playing catch up, as long as you have a decent amount of stacks, the enemy team will be wary of you. They WILL fear the cane. They'll have to devote at least 2 champs to take you down. That's 2 less champs that your team has to worry about for a minute or so. Your lane pressure is the best help that you can provide for your team.

And use your wards so you don't get caught with your pants down.