who are you running in your clan boss team already, im pretty excited for you already seeing who you have 

I would max Skullcrusher. He'll last you until you get one of the absolute best legendaries (Valkyrie/Martyr), and he's very good everywhere else.

Mm, skullbreaker, romero, athel and yag

But i will be the first to admit i dont have a. Clue what im 

skullcrusher definately & frozen banshee definately best poisoner matched with skullcrusher 

plus skullcrusher counterattack champ double your chances extra poisons and damage up

im running slow counter with skullcrusher and frozen banshee still in my ultra cb team solid champs, banshee is a clan boss beast with her kit from hard cb to ultra cb

For arena, the obvious picks are High Khatun for speed aura and speed/TM boost (get her FAST - as in, 250 if you can), Stag Knight for decrease def/attack and Elhain for nuke after HK and SK did the preparations. 

For the fourth spot, you have several viable options including Spirithost (increase attack, so SK and Elhain will do more damage), Miscreated (AOE stun, team support) or Inquisitor Shamael (single target nuke which, if it's a kill, will put the very powerful true fear debuff on the enemy team - he'd be going last after Elhain probably). But Shamael requires quite good gear, probably he's more of a long term project. 

Speaking of gear, your Miscreated's gear is really very bad unfortunately. Sure, he has high HP, but he is super slow, low crit rate and low accuracy - so he'll rarely take a turn, his AOE hit won't do much damage, won't put a big shield and will probably fail to stun anyone as well. Of course, that's partially because you have common and uncommon gear, but probably you can do better already with the gear you have, if you prioritize right. Rule number one of gearing: in 98 percent of cases, the boots should have Speed as main stat. And rule number two: main stats and substats are more important than set bonuses, so don't be afraid to break up a set and use pieces from random sets, if they have superior stats. If your gloves and chest don't have HP percentage as main stat, replace them immediately. For the substats you'll want accuracy, speed, defense percentage, crit rate and crit damage. 

Where is the best place to farm high rank gear? L9753 thanks for the 

You  should  build  up  Frozen  Bashee  ASAP

She  will  be  your  main  poison  hero

Dungeons. Dragon's lair is generally the most straightforward one and the one people start focusing on first. 

I would 6star stag knight next. 

I would not level spirithost personally as you will dump her eventually, i would in arena do

High khatun- go first and turn meter

Stag knight or Armina - decrease defence (i love armina as she lands stuns and turn meter so often but others prefer stag knight)

Elhain- Nuke

Inquisitor shamael- clean up and also protection against debuffs, would love one of him gratz for pulling!

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For clan boss Frozen banshee is a top poisoner - well worth investing early.

I should have clarified why I said Stag.  I don't think you will use long-term in CB or Arena, but you will use in ALL Dungeons, and is useful in CB/Arena until you are at a point to build specialists.  Basically Stag you can use on every team including doomtower.  60 and book imo

I  agree  with  Trips,  i  prefer  stag  over  Tayrel  in  all  dungeons,  unless  affinity  forces  a  change.  

And  as  Trevor  Wilson  said,  Frozen  Banshee  is  fantastic  for  CB.

I  would  also  recommend  Steelskull  for  CB.