Investigating the specs of the gb’s and what you need goes a long way.
Besides Alcatraz, Arc and probably dynamic tower I’d consider to focus on what your era has to offer because that makes a lot of sense.
Especially taking into account what space we gain per era and the fact we need spare room for fp-givers to fill the gb’s.
Also the amount of fp’s you are able to spend likely increases per era (space) so if you have high end gb’s early in the game which are often huge and do cost a lot of fp’s you’ll block your possibilities drastically.
Take for example Chateau Frontenac I think you don’t want to miss out on that one but it makes more sense to build it in the Progressive era indeed.