What accessories do I need to make great espresso at home?

Essential accessories: (1) a quality burr grinder (biggest impact), (2) a digital scale with 0.1g resolution for weighing dose and yield, (3) a bottomless portafilter for diagnosing technique, (4) a WDT tool for distribution, (5) a tamping mat, (6) a knock box for grounds disposal. Nice-to-have: a shot timer, a milk pitcher with thermometer, a calibrated tamper. You don't need all of these on day one — start with the scale and grinder.