Without a scale, making coffee is like making cake without cups. You'll never get good, consistent coffee without a scale. At a minimum, you want a scale that can weight 2000g with a precision of 0.1g with a large plate.
This Hario scale has it all. Great for both espresso and filter coffee. Its large enough for you to put the portafilter from your espresso machine straigh on it. It also includes a timer, great when you prepare a pour-over.