I agree with @deadhead1000 for the most part- one item I see missing from the response was a mock up/prototype. Not sure if you’re idea is based from a test piece or if it’s just an idea but having a functioning device (just enough to demonstrate the idea) is very helpful when it comes to approaching higher level experts and even patent attorneys.
Even if your idea is not the first of its kind it may be its difference’s that separate it from prior art. Again having a working piece helps those professionals you approach narrow down exactly what you need and helps you determine costs and so forth.
Patents are a funny thing- I have applied for a few, have only gotten one to go through. The process can be expensive, the narratives grueling and are very time consuming.
The business plan side of what was first mentioned will be necessary at the right point in time especially if you’re seeking investors but if you truly feel your idea unique (be it an application or invention patent) I would first focus on how to prove it works and then to demonstrate it. You can do all of this while protecting your idea. Once you have this accomplished the rest of the picture will become clearer. Of course if you have deep pockets you can always bring in an attorney, draw up binding NDA’s and search for a company that can develop a prototype for you.
Good Luck!