Make sure it powers on and variable speed works. Make sure it is stopped completely before trying to run in opposite direction. If that don't work (and it's not simple fix like the fuse), I wouldn't spend any more on it, unless you get a free treadmill due to the missing cross slide parts.

Chuck wrench $15 ebay (needed to tighten the chuck to hold your work)
Carriage feed handle (needed to move the carriage along your work)
Carriage 1/2 nut lever handle (needed to engage/disengage the carriage from the feed screw)
Cross slide screw, mounting, handle, other parts? (https://littlemachineshop.com/produc...ss+slide+screw)
and a bit would get you cutting

Change gears - Threading
Threading Dial Assembly - Tells you when to throw the 1/2 nut to engage the saddle
Outside chuck jaws - Holding larger work $20ish if they luckily match your chuck
Dead center - holding longer work. $10ish, a live center $25ish
Drill chuck and arbor - Dead center isn't much good if you can't drill the center
Tail stock - makes those prior 2 things useful
misc hex wrenches, tools, oil