Way back when I got my Go Cutter, I wanted it mainly for shapes that are so hard to cut by hand, stars, hearts, circles, birds, flower shapes, etc. I can still cut strips using the Stripology ruler by Creative Grids, squares, etc. So haven't bought any of those.....yet lol. I have bought dies for specific patterns, Feather tree, apple core, orange peel. For me the dies are too expensive to buy "just because", so I buy as I have a need for them. I am pretty sure that Accuquilt has some rules about sales and you hardly ever see the dies on sale anymore. Unless Accuquilt runs the sale on their website.
So as so many others have said, buy the ones based on the quilts you want to make. The Accuquilt system is really outstanding and has made a difference for a lot of quilters.