I started with the basic's. The one it comes with. (5" 2.5" and 2.5" HST) I have a couple of the shape dies and bigger dies. Not to many though.
I find I love the tiny dies the best. 1.5" triangles and squares.
I find I can cut the bigger sizes accurate just fine.
The smaller cuts don't always have that consistency. So, the tiny shape dies are my favorite.
I actually have two cutters. Accquilt and Sizzix Big Shot. I always use the tiny dies on either of them the most. And, both preform more or less the exact same. So, both are good brands. (One was a gift, one I already owned.)