I have the hand crank Go and love it. I have some physical issues that are not getting better and I sliced myself with the rotary cutter bad enough to give me a real good scare, so I'm coming at it with the mindset that I will use the Accuquilt for everything I possibly can (and hopefully keep all my fingers while making all the quilts I want!)
I tried to give some thought to what dies I'd use the most based on what I like to make already and what I want to make within the reasonable future. If I liked applique, I can see how it would be easy to spend a ton on dies that may not get used much!
I started out buying strip dies in the sizes I used most. Strips are used on their own often enough and the strip dies have lines printed to align for cross cutting, so they are pretty versatile to start out with. You can always cut the strips further with a rotary cutter if you need to. I've added mostly squares and half and quarter square triangles in several sizes as I found patterns I wanted to make. I like traditional quilts, I like to make Bonnie Hunter patterns with tons of small pieces, and I don't really enjoy applique. I've bought the log cabin die and double wedding ring die since I want to make both of those quilts. I know the log cabin isn't especially hard to cut when compared to other things, but I'm currently working on a queen size memory quilt in denim and heavy pants materials and that top alone was worth the cost of the die for me. I'll probably buy the storm at sea die as well once it's no longer new enough to be excluded from their sales. I would have never attempted hand cutting a double wedding ring, but I'm planning one in king size now that I have the die.
I am another person that doesn't care much for the cubes because they often only cut 1 shape per die rather than multiples. If you are the type of quilter who would enjoy them, they look to be pretty handy. Out of curiosity I've looked at a couple of the cubes against the dies I already have and I'm really only missing some odd shapes that I haven't needed for anything I want to do. Those pieces might be important to you though!
There are always sales of some kind going on at the accuquilt site. I also am not shy about reviewing anything I've purchased since that earns 'points' for their reward program. The app is great too, especially if you shop for dies outside of the site. It helps keep track of what you have already, but you'll need to manually add anything you don't buy from Accuquilt's site.
I think I've got nearly anything I'd ever want to cut, but I'd love to see what other people are finding to be useful! I have actually bought a die based on something I read here and I'm happy someone shared that info.