So I'm thinking of trying to get into Beasts of Chaos. Any general tips or units to avoid? Where's a good place to start?

And since I have most of a Daughters of Khaine army, what's a next step given I have:

Morathi
Bloodwrack Medusa
Hag Queen

30 Witch Aelves
2 units of 10 Blood Sisters

1 unit of 5 Blood Stalkers
2 units of 10 Heartrenders

I guess the obvious answer is beef up those Blood Sister units. But is there another better next step, or have I got basically everything the army has to offer?