This will depend so much on your current audience and your genre. But all reviews are is making connections with people who are excited about your book.

Creating a mailing list helps you get people on board, and you can then ask for favours like for them to leave a review in exchange for a free copy of the book.

This will also depend on your goals in publishing (i.e. to get information out there, to publish a book you're passionate about, or to try to earn a living), but you get better with time, practice, and building an audience. Your first book might not get as much traction, but building upon that with subsequent releases will help grow your audience, and the number of reviewers you have on your team.