Solid base layout vs. building facilities as required

[Icarus]

When starting a campaign and building facilities, I basically see two options:

1. Make sure the workshop is situated within facilities that can use engineers, like resistance comms, proving grounds etc. This necessitates building facilities in a certain order, as each space needs to be excavated first.
My current setup is
AWC Relay GTS
Comms Workshop PG
Other stuff

The consequence of this is that I can't build psi chamber and laboratory for some months.

2. Build facilities as they become useful, i. e. build laboratory and psi chamber on second row. More immediate advantages from the buildings, but no obvious use for the workshop.

What do you consider the more useful approach on commander and legendary?

[Saph7]

The workshop only needs to be adjacent to 3 engineer-using facilities. Even 2 is okay if they're ones you're going to want permanently filled after a certain point (e.g. Resistance Comms). So it's fine to use a workshop-adjacent slot for a GTS or whatever. For training and research buildings, the sooner you can get them up, the better.

[Icarus]

The lab is also one of these buildings that benefits from being built on a coil. Which would mean a delay as well. Same for other coil candidates like Power Relay and psi chamber. Can I get by with just one PR if I do not build any of the mentioned facilities on a coil?

[LordYanaek]

There are 2 really power hungry facilities : the Lab and Shadow Chamber. If you build both on coils you can get with only 1 relay which will leave an empty room in the avenger so it's not terribly useful especially now that facilities don't have an upkeep. I think you can get with only the Shadow Chamber on a coil (it comes rather late so you have time to dig) but if the you have a coil on L3 it's probably a good idea to put the lab there as you'll be able to add stations when you get scientists to staff them without possibly having to wait for a a power relay upgrade.
Depending where your coils are, it's also probably a good move to build the workshop on a coil as it will give you +7 power which is enough to give power to a several important facilities earlier than you could build a relay.