This achievement can be earned relatively early in a campaign so long as you focus on upgrading one particular settlement. However, it may be unwise to do this and neglect others, so it’s probably better if you do it gradually as you expand your faction. You can invest resources into one particular settlement that you want to see grow to its full potential, constructing everything available there. As your faction grows, new projects will become available for specific settlements, so you’ll need to check back every so often and keep building things!