You're kinda early for that, so for now just run your highest level and best geared champs. Eventually, you'll probably be building something around Grizzled Jarl, Rearguard Sargeant, and Ronda. But for now you're missing someone who can bring Leech, and someone who can deal with the debuffs.

for clan boss get poison champion or hp burn champions

how much damage you do now

I'm not sure what difficulty CB you're doing, nor do I know who has gear/scrolls. Based on what you have:

1. Ultimate Death Knight (Tank/Support)

2. Rearguard Sergeant or White Dryad Nia or Kunoichi (Support)

3. Ronda (DPS)

4.  Frozen Banshee

5. Gravechill Killer

You would need to pair Banshee and Killer specifically to get/maximize your poisons, you don't have any other good poisoners that I see. Ronda and UDK with Warmaster (Giant slayer for Ronda optional)

UDK would offer shields and heals, neither great but better than nothing

All 3 of those supports with ally protection listed have their place, but Rearguard would be best for Decrease Attack and Defense on CB plus she somewhat heals on her A2.

But yeah, like the others said, you don't have many options for a good team (yet) however keep at it and you will. You've got a Painkeeper so if you get a Maneater you can make a unkillable team