Also more specifically some general advice for Nasus would be good. I'm not sure what gear to get, lifesteal?
You generally build him at least a little bit tanky.
There were some revamp recently, nerfing the armor and magic resist items (so the HP ones are enhanced now), that nerfed him :
Having passive lifesteal let him regen HP, which is better if your HPs last longer (having armor/MR), and his ult give him more HPs, which is better if those last longer (having armor/MR)....
The doesn't have any control outside of his Slow, and is not a carry, so he usually get a Randuin, to boost his armor and controls (and having some HPs is always nice, anyway). I didn't play since the Banshee's veil changed, but I think it would fit him well. As for boots, there is choice : If you want to gank often, mobilities are very good (and his slow is long so it's a good gank utility). If you are against a big physical damage dealer in lane, you'll want the tabis. If you're against a big controler and their jungler have real disables too, you'll want mercuries (remember than the 450 gold spent to make mercs from boots & MR item nearly only gives you tenacity, which may not be worth it on lane, if the controls aren't what kills you). Finally, if their controls are mostly slows, you'll want the swiftness boots, as they'll greatly reduce how muck kited you get.
As for lifesteal items, you generally don't need them : Even if it is not capped (except maybe at 100%), you are not here to build 4 bloodthisters
Some items are good with nasus, because of how they work :
- Randuin, as stated above, for the HP, armor, and passive + active.
- Iceborn Gauntlet gives you many things you want (mana to cast a little more, CoolDown Reduction (CDR) to spam your abilities, armor to tank more, and the passive will boost your Q : you'll be able to deal great damage in a zone, and killing many minions with it will give you the boosts from all the kills.
- Sunfire cape is a good item if you're not doing bad in the game and you still want to tank more physical damage : the HP and armor obviously are good, and the passive will help you deal damage to all the ennemies in teamfight or push in lane.
- Banshee's veil, if you need some Magic Resist (MR), and you'll need some if their APcarry isn't total garbage.
- Abyssal scepter : If you're already doing good, and your APcarry didn't build it, it will enhance your MR, your damages from ult and E, and the magic damage of your whole team.
As Nasus, you're supposed to be the main frontline in teamfight, protecting you allies from pokes and engages from the ennemy team. To do that, you'll need to be able to take some damage, and you'll want to be able to retaliate quickly, hitting ennemies with your Q and auto-attacks.
PS : I haven't played Nasus for a while, so some advices may be a little outdated