This is my build when i go top, and most of the time i build it in that order. i generally buils the right side of frostborn first, starting with a saphire crystal. the frostborn gives me a bit of extra armor and cdr, plus the aoe lets me farm better. deadman's i buy just to tank me up and make my q even more dangerous, most of the time i have about 250/300 stacks by the time i can buy it. then i build trinity or black cleaver, depending on how the game is going. if i need more damage or a quicker item to turn things around, i build black cleaver for the extra health and to cap out my cdr, which, with my runes & masteries, puts my q at 2.8 seconds. if i can take my time, however, i'll probably build trinity force, just because the extra mana is helpful, and it allows me to be a real presence in teamfights, slowing one person, killing them, getting that movement bonus, slowing the next one, et cetera. Then i build bloodthirster to make my q a little more powerful, but really more just to stack onto my passive lifesteal and give me that sheild so i'm a tad tankier. last but not least, i build warmogs to turn myself into a total tank.

your early game does matter. it's pretty easy to get back into things as nasus, just go play farmville if you're slacking, but if you can outfarm the other toplaner in the beginning and just leave them alone, ignore them, you can really scare them with your q about fifteen minutes in. generally, i upgrade e,q,q,e,q,r,w,q,q,e,w,r,e,w,e,e,w,r. i get the e first to give me both that aoe to help me farm and that longer range poke to keep my opponent off my back so i can farm better. i then like to max my q as soon as possible so that when i do finally whip it out, it does some spooky damage. i don't generally get my w until after i get my ult, (lv.7) just because i'm not going to use it until i can ult and just shred them. up until level seven i don't touch turret, i don't really mess with the other toplaner unless i have to, i just farm. once i get my second kill or so, i start pushing, i start going mid to help, i may take dragon or rift herald, depending on whichever's closest.

nasus is a snowballer. most of the time, if i'm not helping out in a teamfight, i'm taking out a turret. nasus also isn't exactly someone who needs to be fed to be helpful. i realized a while back that it's much more effective to let my teammates have the kill and let them get fed than to make myself get super fed. nasus gets fed off of farm, he doesn't need kills to be a real presence on the map. part of the thing that makes him so great is the fact that he can duck in, take out a turret, and be gone in a good ten seconds. he's great at opening up lanes so that minions can push top and bottom while we're all mid teamfighting. this also forces other members of their team to go take care of minions if they stack up, allowing the teamfights to be won fairly easily. i generally go about half as many kills as deaths and so many assists they're falling out of my pockets in waves, with a good majority of the turrets taken

i'm lv 18 lol, i haven't even really finished out my rune pages just because i want to wait for level two and i also barely got my keystones