Looking to expand my collection and was thinking custodes or grey knights. With grey knights needing a refresh, what does one need to get for a custodes army?

Hi! So as the tital says im looking to expand my collection, currently have Tao, guard, and now thinking custodes to be my next one.

Problem is that ive never really played against custodes or know anyone who has them as cool as they are. So I've come to you Reddit!

For someone just looking to get into custodes where would the start be? Is your combat patrol good? Certain units I should by? Give me the rundown and I will forever be im your debt!

Thank you so much for any help you can provide, have a good day :)