Run 50ft underground electrical: gauge and conduit?
A 20 AMP breaker you can run #12 but if you're going to install the PVC conduit, use 3 #12 THHN/THWN-2 wires, black, white  &amp; green. You don't need the direct buried cable when using conduit. If you can feed it from the box your existing GFCI is in, then you could connect to the load terminals of it. If you're connecting elsewhere you'll need a GFCI outlet at the termination of the run. 1/2" conduit will be right for your job. Stay away from using backstabs and if you use stranded wire get heavy duty outlets with the screw back clamps.