So are you trying to make a nurgle list or the best list possible?
If you're trying to make this best list possible take 6 heldrakes, typhus, and 5 groups of 35 zombies
If you're trying to make a balanced nurgle list that is fun to play as and against, this website is a terrific guide to each units strengths and weaknesses
http://bloodofkittens.com/blog/2013/02/24/tactics-final-chaos-space-marine-breakdown/ As for my opinions,
id say the best out there are autocannon havocs, plague zombies, plague marines in rhinos with 2 special weapons, obliterators, baleflamer heldrakes, typhus, biker lords/sorcerers escorted by chaos spawn, raptors/bikers with melta equipment, and tri-las predators.
As you can see, the fast attack section is really bloated with powerful units. No matter what
CSM army you make, you generally want to fill out all 3 fast attack slots.
Dark Vengeance is a good place to start.
a 500 point nurgle list
id take
Chaos Lord- Mark of Nurgle, brand of skalathrax
Helbrute
10 cultists-shotgun, flamer
10 cultists-heavy stubber, 9 autoguns
7 Plague Marines, rhino, 1 plasma gun (lord goes here)
You can get all that with just the
DV kit and a kit of plague marines, and it will all be what you see is what you get, except for the plasma pistol on the lord.
a 1000 point nurgle list
id take (this means you're more serious about this army, we're not going to add, but change the list)
Chaos Lord-
MoN, bike
4 Chaos Spawn-
MoN (Lord goes here)
7 Plague Marines- rhino, 2 plasma guns
7 Plague Marines- rhino, 2 plasma guns
Heldrake- baleflamer
Helbrute
I wouldnt take the helbrute at any point games after 1000, thats where he really starts to lose value. Start to add heavy supports after this point. Lots of havocs and oblits and predators.
Good luck!