I started Nurgle CSM and then added Daemons and they've helped a ton. I switch between CSM and Daemons as to who gets the main detachment. It's been running pretty well. After ~1000pts of Daemons he can fit in ~500+ of CSM with some minimal cultists, a biker HQ and some nurgle bikers.
It is way bigger than you are looking for but here is my Nurgle list with CSM as the lead:
Nurgle csm CAD
*HQ*
Daemon Prince (315pts)
>2x Mastery Level (become Psyker), Nurgle, Power Armour, The Black Mace, Wings
Sorcerer (98pts)
>Combi-bolter, Force Sword, Spell familiar, Bike
*Troops*
(158pts)
2x 10 Chaos Cultists (79pts per)
>Cultist Champion, 9x Autogun Cultists, Mark of Nurgle
*Fast Attack*
5 Chaos Bikers (200pts)
>4x Chaos Biker, Mark of Nurgle, 2x Plasma Gun
+ Chaos Biker Champion
>Combi-plasma, Lightning Claw, Melta Bombs
*Heavy Support*
3 Obliterators (228pts)
>Mark of Nurgle
Allied Nurgle Daemon Detachment
*HQ*
Daemon Prince of Nurgle (370pts)
>Corruption, 2x D6 Greater Daemonic Reward, D6 Lesser Daemonic Reward, Daemonic Flight, Mastery 3, Warp-forged Armour
*Troops*
6 Nurglings (90pts)
*Elites*
Beast of Nurgle(52pts)
*Fast Attack*
5 Plague Drones of Nurgle (260pts)
>Death's Heads, Venom Sting
*Heavy Support*
Soul Grinder of Chaos (180pts)
>Phlegm Bombardment, Nurgle
2000/2000