How long is the run? I went with stranded THWN wires inside pvc conduit. You aren't supposed to run UF through conduit for a long run, though I don't know if code approves it or not.
Code says for sch. 40 pvc conduit the trench has to be 18" deep for a non-GFCI circuit. You only have to go 12" if your circuit is protected.
I also ran a piece of twine throuh the PVC as I assembled it. I used a swing elbow to bring the pipe & string right into the hole in the bottom of the lamp post. Then I duct taped the 3 THWN #12 wires (black, white, ground) to the string and pulled it through while a buddy fed it from the other end and lubed it up real nice with wire lubricant
Don't run the wire through as you glue, the glue can deteriorate the wire insulation if it makes contact. And do yourself a favor and get stranded wire (not solid), it's way easier to pull.
You can direct-bury UF cable, but after having to dig up and replace a whole run that was done that way (by the last homeowner) due to a tear somewhere
in the wire...I'll never do it myself.
Here's a pic of my conduit leaving the basement wall, with the string sitting there waiting to tape up the wires: