There is no ranking of “importance” for editing—only an order in which they are usually done (Substantive and/or Dev first, line editing next, then copy, and finally proof.) Your manuscript needs what it needs. Here’s how I would approach it:
If you are not a trained story-teller or writer; if you can’t explain what a plot point is or have never heard the terms character arc, story structure, theme, or internal/external conflict, hire a developmental editor first or AT LEAST. This person will get your story in order. Skipping this step and going straight to copy editing is like putting a fancy coat of paint on a car that doesn’t run. Save the copy editing for last. Dead last. Just before querying or putting your novel up on Amazon (or wherever).