A/B Tests aren't for every website. If you have a high value item that only 20 people see a week, but when it converts it means a bigger return, A/B testing would be a lot harder to implement in a way to get return on investment. A/B Tests and multivariate tests are perfect for websites where you have a solid amount of traffic coming in so that you can reach statistical significanc.
Two of the crucial moments on a website are when a visitor lands on your homepage and product page/buy button. So many of the case studies, I've read and implement changes around these crucial areas....
5 test you should do.