Production licences, how many do I need?

I am trying to work through some indicative pricing. One of the things I am struggling with is how many licences will I end up needing? I know I can start with 9k but I don’t want to end up going back and beg for 5 times that…

Q1. the licence is per environment. Traditionally we have run 3 environments minimum, how many environments are people running for their API management?

Q2. No. of Gateways; How many gateways are recommended to service your public cloud instance (Azure for arguments sake?) Two load balanced?
NOTE: As I have 3 different clouds to support this multiplies the no. of gateways by 3.

Q3. Does anyone have any good links to reference architectures they could send me a link to.

Thanks!