Well there are a lot of variables to think about. Are you able to crank a handle or would you prefer an electric cutter? Are you okay with buying multiple dies with pre-set shapes and sizes, or would you rather be able to cut your own custom sizes and shapes? What is your price point?
Some people are happy with the hand-crank Accuquilt Go, it's an affordable basic machine that comes with a couple of basic dies. Extra dies are purchased separately. On the other end of the spectrum are machines such as the Brother ScanNCut, which can custom cut any shape your little heart desires, but runs about $400.