For someone who hasn't DMed before, you definitely want something where the adventure is well mapped out and moves from point A to point B, to point C, etc. I have played and DMed several of the Adventure league modules from the first season and found them to be pretty decent for the most part. They are short, they can be played stand-alone, but if done in order, each one leads into the next and there is XP guidance and play level guidance and how to adjust the adventures based on strength of the party. The biggest issue is finding copies of them. You might want to ask your local D&D store if they have any AL content and if they would allow you to play older seasons.