Best sequence for building/managing servers with Puppet?

I need to both build some new servers and rebuild some existing ones
keeping in mind I want to use Puppet. The question is which is the
best sequence to proceed with?

A) Develop modules one by one and make sure each component works, then
assemble and test modules that need to talk to each other and make
sure those work together, all *before* building the servers. Then once
all the modules are completed and tested for each piece of
configuration and functionality needed at the systems level they can
be used to build each server automatically.

B) Build the servers manually first and retrofit them with pre-
existing Puppet modules, hoping that the modules will just work AND
match how each system should be for your particular needs.

C) Build the servers manually first and then develop the modules
needed to manage each one.

Is there one way that saves more time? Is there one that lends a
higher degree of confidence everything will work as expected at the
end?