Heroes Questions

I know meta changes frequently but what's the best currently:

1. Assuming I have all 6 heroes max, which 4 heroes I will be using for air attack and ground attacks?

2. Which equipments are the best for minion prince (I don't have dark crown only)?

3. Which equipments are the best for Diddy dragon duke?

I am f2p so I have to spend my ores wisely for minion prince and DD.