This question, I feel, may best be divided into 2 categories:
academia and practicality.
For a derm resident, the must read journals are:
JAAD, Archives, Derm Surg, Pedi Derm +/- Cutis, J of Drugs in Derm, Cosmetic Derm (and I may add that Derm Times and Skin&Allergy publications are nice summaries as well)
Those in Academia may feel that the following are necessary:JAAD, BJD, JID, Archives
Let it be known that the JID is a very respectable publication for basic science. However, I can never seem to get past the abstract of the 1st article I try to read in it. It does have a nice 2-page summary of important articles in the beginning that may ultimately wind up on future boards/inservices.
As for what to publish and where to submit, my first recommendation to those future applicants is to publish in respectable journals as frequently as you can. Furthermore, 3 case reports in Cutis do not equal a long basic science project that eventuates in publication in the JID (despite where your name falls on the author list) nor will a review in a throw-away journal equal a CME in the JAAD. Non-derm publications may add to your CV depending on content/place (articles in the Lancet or Nature, I assure you, will not be frowned upon come interview day).
Obviously, the examples I mention take a lot of time, which is why many must take a year or two off before applying. I will add that published articles are almost always better than not having anything published or submitted.