I say
1. Brutal 12.3
2. Arena (this may adjust priorities)
3. Dragon
4. CB
I don't have madame, but she is used frequently in gold4. So I may move her up after apo. If your 1st 60 can farm 12.3, apothecary should be 2nd. Easily booked and you will use on every team for a long while. Getting the arena medals flowing and GH upgrades sooner is a big plus. Especially since it keeps the progress missions moving quicker.