CoC - Best Fire+Lightning spells for it?

So, I love the idea behind Cast on crit. I heard it isn't as good anymore with the exception of Discharge/cospri, but even if it's sub-par, I want to make a build around it in the future. I got a baseline of the gear I'm gonna use, but having no idea about the mechanics other than getting high crit and high attack speed and scaling damage afterwards, I'm curios on what gem setups would be good for fire+lightning skills? Or rather what fire and lightning skills would be best for clear, best for single target, etc.

So far I'm leaning towards magma orb+spark, than have a cold claw proc EE, but unsure how those skills are for clearing (and can't test). Is there better skills to use? interactions i'm missing? fireball? ball lightning? flame surge for single target? the acsendancy would be elementalist to avoid ele reflect.

Things that make a spell good for CoC:

-Doesn't need precise manual targeting (so shock nova, spark, ark are all good, whereas storm call is bad.)
-Low cast speed or high mana cost normally (so casting it automatically is better than manually. eg: fire storm is better than flame surge)

Other than that, you would want to pick skills that share support gems. So for magma orb + spark you could use faster projectiles, elemental focus, or controlled destruction etc.

I've never seen magma orb CoC but it sounds fun. Of course, any skill can work well if you build around it. You can make CoC storm call + flame surge if you really want to.