Luke was a full fledged Jedi, He just wasn't as flashy or as fast paced a fighter as the Jedi Order before which had the luxury of being able to study each other's form of Light saber combat styles and stances. All Luke had was what he could find along with what Ben and Yoda could tell him or show him. It was enough however. He was still a formidable opponent for non force users and Darth Vader. As can be seen in ROTJ.
I have a feeling if Luke had went up against a Prequel Jedi in a sparring match he would get his butt handed to him though.
Not entirely sure on that, remember he could learn stuff on the fly from watching others. So if he sparred a jedi knight from the PT era, he could quite well hold his own and perhaps beat the knight.