The publisher will not help you at all when it comes to design and data modelling. Start without Publisher!
But as soon as you start discussing automated refresh, distribution of multiple documents to different users (or same document but with different data sets), security (who gets to see what) and governance (IT needs to be on top of these things), then the Publisher can help you a lot. If these things are important, then you are better off if you buy also the publisher and start off planning also these things. Start with the Publisher!