Chaos 8th ed. Army building thoughts.

So I havnt played 40k for quite a significant amount of time, the last game I had was in the early days of 5th edition. I've been playing some other games in the meantime, bolt action, frostgrave, dystopian wars etc but I'm looking into getting back into 40k for 8th edition.

To do this I'm looking to build a Night Lords themed CSM army, I wanted this army though to be fluffy to also be as competitive as possible. I've only really got a few bits at the moment, 5 raptors, a CSM squad and a terminator lord however I'm looking into ways to expand this and thought I'd ask you knowledgeable guys.

My thoughts going forward are to get a start collecting box and a few other bits now I just wanted to get some idea of where would be good places to expand my army beyond this. So far I was thinking of picking up a rhino and I'm torn between getting a box of terminators, a squad of bikes or a squad of havocs/a vindicator. What my question to you guys is what would probably be the best to get moving forward.

I also wanted to get into some discussion on Chaos tactics in 8th ed in general just to better help me understand what I'm jumping back into.

Cheers guys and much love.