New to the hobby, never played/collected 40k before but I recently bought a fairly large lot of CSM stuff. Pic is only guy I've painted so far. Looking for advice/recommendations on how to turn this into a 1000 (or 500?) point list so I know what to prioritize building/painting.

I have:
Legionaries x20
Legionary kill team upgrade sprue
Legionaries from Shadowspear x15
Cultists x6
Possessed x5
Master of Possessions
Chaos Lord
Dark Apostle
Sorcerer
Demon Prince w/ wings
Forgefiend
And also a dreadnought I want to turn into a helbrute