Tm vs opening up new maps?

What's better to use energy on?

I am skipping team mode until I'm on the third floor.

A) Team mode is 60 energy!
B) I don't know how to get skill books so I hope Expert maps on the third floor answers that question
C) TM mode seems to be unavailable most of the time, I'm not sure the requirements to access it, but it's on cool down 95% of the time without me doing it.

It's not on cool down per say. It's only available every 2 hours for 1 hour at a time. I think this is an incredibly stupid rule but meh i'll just keep running expert

I do to now when it unlocked but I got a new mode called "Challenge Mode" or something like that. It seems to only offer XP cards and has Normal, Veteran and Expert difficulty leaves. From what I can tell this is more like the Team Modes from HM. The individual battles feature much better rewards and scale pretty drastically in difficulty, expert mode has all Epics with advanced skills and in complementary weather.

I haven't actually one yet so I don't know the final rewards, but the XP per individual battles is much higher than the Tower Modes.