The 1868 edition contains all the poems that are now commonly used.
Before we start, I would thoroughly recommend that you visit this website devoted to Les Fleurs du Mal, where you can consult the full text of the different editions, along with a variety of published translations. The 1868 edition contains all the poems that are now commonly used. As all the translations on the site date from over 60 years ago, you may wish to buy Anthony Mortimer’s stylish and clear modern translation; it is available as an e-book or in traditional book form and comes with the original French versions.