How much money do you have to spend on your release? Do you have skills in cover design, formatting, editing, proof reading, social media marketing, or promotion? Do you have connections with bloggers or reviewers, or understand what you'll have to do to grow a fanbase? How many books are you planning on releasing? How fast do you write? What genre are you in?

Self publishing is more than just hitting publish on a book. It's a lot of various skills that require a lot of time -- or money, if you want to hire it out to others. Having a professional team behind your book could be an absolute boon, and publishing through Penguin could give you a lot of respectability in certain circles.

I exclusively self publish right now, but I'd say only 10-20% of my time is spent publishing. The rest is handling all the marketing, promotion, graphic design, formatting, web design, etc. that self publishing requires.

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.

You can put your book for free on multiple vendors (Barnes & Noble, iBooks, Google Play) and try to get Amazon to price match, or use KDP Select if you want your book exclusively on Amazon.

Another alternative, though, is to give out Advance Review Copies to your supporters. These reviews are weighted less heavily than verified purchased reviews, but they'll still show up on Amazon.

Most people have success rates of about 10-30% of people who receive an ARC actually leaving a review, but this is hugely dependent on genre and your relationship with your review team.