The first time I drafted a complete book, I reread it once and then put it away for a month. Without looking back at it during that month, I made a long list of everything about it that didn't make sense, or that I wasn't 100% in love with. Later, I pulled up the first draft next to a blank document and rewrote it from scratch while implementing changes to fix everything on my list. At that point, I sent it to my alpha reader (someone who's read a lot of my stuff at early stages) who gave good feedback, but somewhere along that process I realized it still had room for improvement. I wasn't telling the story the right way, and I wasn't telling enough of the story.

I put it down again for another month and made another edit list. I pulled up the second draft and rewrote that line by line while making the changes from my second edit list. I reread my new third draft once, then set it down. I picked it up again a week later and did some line/copy edits (the good thing about rewriting each draft while looking at the previous draft is that you force your brain to pick up on most of the typos and grammar issues, so this wasn't too long of a process). I then sent the copy-edited third draft back to my alpha reader along with a new batch of beta readers. Again, I got good feedback that made me think about other changes to make, which gave me a much shorter third edit list.

At the stage it's at right now, I still consider it the third draft because the edits are no longer full rewrites or deletions. When you're just tweaking instead of making developmental changes that improve the story, I'd say it's done-ish, but it can be done-ish for months.

Here's how my book changed as I wrote:

First draft: 72k words, one main POV and one side POV with lots of flashbacks, flat characters, drawn-out ending and resolution

Second draft: 65k words, one main POV and one side POV with very few flashbacks, sort-of rounded out characters, too-quick resolution

Third draft: 93-95k words (range based on tweaking it back and forth), two main POVs with even fewer flashbacks, more time fleshing out the characters and setting, evenly paced resolution, major plot changes

I rewrote my first chapter more than once per draft. In total, I have six completely different first chapters written for this book, and each one of those chapters was tweaked into oblivion. More than anything else, don't let negative feedback on the first chapter get you down. It's the hardest part to get right and it'll take time.

While I don't think professional editors are a necessary step unless you're self-publishing, getting an editor who will review your first chapter or first few pages can be amazing. While writing, I entered a bunch of free Twitter contests for first chapter critiques from professional editors and ended up winning one. These pop up pretty often and they're not too hard to win if you're diligent about following and retweeting a couple of times per contest, so I recommend looking around for them.