A provisional patent application is a stepping stone toward a utility patent. One effective strategy for using a provisional application is to establish your priority at the patent office at a lower cost that that of a utility (non-provisional) application, so that you can go out with the idea, talk to people about it, and see if it’s worth the investment to file the utility patent application.
If the invention is finalized, and depending on the subject matter of the invention, so you may want to pursue a non-provisional patent application to begin with. If you’re still refining and developing your invention, you may want to consider a “staged provisional patent application strategy” — by filing multiple provisional patent applications, then a non-provisional patent application.
A PCT patent application is a convenient way to initiate the process of applying for patent protection in multiple countries, and allows you to defer costs while you work to perfect your product, and assess the market fit. However, if you are certain that only one or two countries will ever matter to you, then you should consider filing only in those countries directly.