After I gather feedback from my three readers, can I send it to an editor or publisher?
No. Start rewriting!
Review the information that your readers have provided and begin to address their concerns. If you can't figure out how to address their concerns, consider taking a creative writing course - if you're writing fiction, memoir, or creative non-fiction. Consider taking a research writing course if you're writing research, technical or trade books, or self-help. The first place to look for a solid and inexpensive course is your local community college. If you've already had those courses and you're just stuck for ideas in this instance, this would be another good time to consider hiring a writing consultant or writing coach for a few hours. Sometimes we just need to talk the issue through, then we can move forward again. Remember, if you go to an editor too soon, you will have to pay professional prices for work you might have been able to accomplish on your own. However, if you are truly stuck, then hire a professional editing firm such as BookMakers.