As far as I can tell, the other-people-giving-feedback stuff seems to go:
1. Developmental/content editor. This is a person with some experience/knowledge of knowing how stories work. They can tell you things like, your main character doesn't do anything except react/your pacing is too slow/you need to tighten
here and
here/your protagonist makes a major logic leap in chapter 6 to make the plot work, and while you're at it, delete chapters 1 & 2 because they don't do anything useful. You can probably expect advice on how to fix the problems.
2. Beta-readers. These are non-professionals. They're not going to give you specific structural story advice: that's not their job. Their job is to be the first 'real readers' to see your story at a fairly advanced stage, and they give you a reader's-eye view of it. Do they hate your protagonist? Is it boring? Did the pages fly by or did they have to struggle to get to the end instead of doing something more interesting, like the washing-up? Did the plot make sense? It's their job to tell you what readers are likely to feel/think when they read your story, not necessarily how to fix it. This may not seem very helpful, but it's vital: after all, your story is going to be read by readers, not editors. You need a 'normal person' view. The real qualification for being a beta-reader is that you love to read.
2a. Some people have alpha-readers, who see the story at an even earlier stage than beta-readers (which is why beta-readers are beta). I'd guess that it's before even the developmental editor sees it. Presumably their job is to say things like, "This is basically
Star Wars, isn't it?" or, "You do realise none of it makes any sense at all, right?" That is, is your story working, even in a very rough way? Sometimes you can be so close to it that you just can't see the major problems, and having a second pair of non-specialist eyes can point you towards big problems you can fix - that don't need an editor's expertise once they're pointed out.
3. Copyeditor. These people look at the spelling and grammar, so they come last in line. There's no point getting all the commas right if you're going to delete the entire chapter.
For
developmental editing, you probably want to find someone with good testimonials: this is the expert who's going to tell you how to fix things. You want it to be right. You also need to make sure that the person likes the kind of story you write: no point sending your sword-and-sorcery fantasy to someone who generally does chicklit; the styles are too different. Unless you've got friends who know about story structure etc, expect to pay.
For
beta-reading, there are quite a few ways to get beta-readers who will read for free.
Goodreads is apparently a fertile source - there's one group called 'Support for Indie Authors' or something of that nature; it's quite big and quite active, so if you join that and ask, they might be able to point you in the right direction. Or some of them might be willing to do it themselves. There are other groups on Goodreads where you can ask for beta-readers too, I think.
For
copyediting, I'd strongly advise you to put your work through something like
Grammarly first - preferably before you send it off to your beta-readers (be nice to them!), but definitely before the copyediting stage (Grammarly picks up more errors more reliably than Word, even in the free version). Every error you can pick up with a computer program is one that a real person doesn't have to pick up. And I know from experience that if a page has twenty errors on it, chances are a human will pick up eighteen and miss two. If there are a lot of errors, there are just so many you can't get them all. The fewer errors there are, the more chance a human will pick them all up. A messy manuscript is just distracting. Plus, if you're paying for copyediting, I think they charge by the hour. The more errors they have to correct, the longer it'll take and the more it'll cost.
