This is such a vibrant portrait, I love the mood! Very impressive for a first oil painting!
My only suggestion is that in the whites of the eyes it helps to use warmer colors. White reflects what is around it, and with all of his warm skin tone surrounding the eyes, it will influence the color. Also, when painting a richly colored irises like blue eyes, pay close attention to warmer colors in the blue eyes, there will usually be a more subdued grey and sometimes bursts of yellows,etc. Since all eyes are different its hard for me to say, but look for as much variation in the warm and cools as you can.
You did this very well in the face, a lovely combination of warm and cool lights. Keep painting, you definitely have a head start!
Thank you very much for taking the time to look and give your advice. I would love to be a full-time painter one day and quite enjoyed the subtlety of the portrait. I am going to work on a landscape next and then might attempt another portrait. I am sure your thoughts will help me improve.