Starting 30k Night Lords!

Hey guys! I am thinking about starting a Horus heresy army for night lords.

So I’m gonna get the starter set, and I think I’ll get the NL Contemptor body and NL heads.

Aside from that, what should I consider?? Is that a good way to start or is there something else I should consider?

Additionally, is there any guides or videos I should check out to get started? What about the weapon upgrades? Are any of those worth it to begin with or should I not bother?

Also, what are the benefits of night lords as an army anyway?

Thanks:)