I am looking for a couple of nouns that describe someone who is noticably improving at some learning activity. If someone is just starting they are a novice or a beginner; at the end, there are various words (expert, master, etc.). I am looking for words for someone who is a beginner, but who is markedly getting better, and for someone who is not an expert but is approaching it. I already thought of improver. It doesn't seem very satisfactory; neither does trainee, which doesn't imply improvement.