We rebuild your highest leverage page and run it as a live split test against the page you have now. Revenue per visitor decides which one stays.
Usually the product page, because that is where the money is decided. One page, rebuilt properly, with up to five iterations if the first version does not clear.
Your traffic splits between the new page and your current one. No redesign without a control, so a good page is never confused with a good month.
After the first win, testing continues as a programme. Fewer opinions, more tested changes, each one measured on your own traffic.
Every figure we publish was measured in an A/B test on the brand's own traffic.