My advice would be to get a board with a primary microcontroller that has native USB capabilities. Those are the boards that use the ATmega32U4 (e.g., Leonardo, Micro, Pro Micro), and the SAMD boards (e.g., Zero, MKR boards). The reason I recommend those over an Uno or Mega with the ATmega16U2 USB to TTL serial chip is that the DFU process is a little bit more complicated. With the native serial boards, you just upload your sketch as usual. That said, if you are trying to follow a tutorial that is written for the Uno then it won't apply to a native USB board.