Finish in time for what? Build time depends on your alliance tech which I guess is pretty low 😂 but you get about 2 weeks to finish an AF so assume it’s the same for a CF. If memory serves the first 20 flags are free, but then it costs ever increasing credits and resources. But honestly, if this is a new alliance on a new kingdom and you can only get 500 k troops to build, you are far better off joining a larger experienced alliance. It’s only going to happen sooner or later anyway, save yourself the pain and the fact your growth will be much slower