A simple tracking method works well here. You might try an Excel spreadsheet to track dates, costs, and methods, or use the Word doc attached here to fill out your details as you move through the posts.
A note about timing: a lot of emphasis has been placed on book release dates, as if that’s the only time to market a book. This is a relic from traditional publishing. Trad publishers have a narrow 90-day release date window in which to sell books. (After that, retailers return unsold books, sometimes a lot of them.) As a self-published author who is selling directly to readers (in many cases), your timeframe is not strict. A new book is new to the reader, not necessarily new to the market.