A couple of things I can think of -- see if you can have him focus more on friendships and just participating in things that he enjoys. As you have noticed he appears gloomy - being gloomy typically does not attract people. If he is out having fun and enjoying himself you just naturally have people wanting to hang with you.
What does he like to do? It could be music, sports, gaming, outdoors? Join a club or activity at college that is centered around his interests - it is a natural way to make friends -- that often develops into girlfriend situations. In any case he will be having fun doing things with people he enjoys. This alone should raise him from being gloomy to being happy and others just naturally like to be around those that are happy and in a good place.
In others words - he needs to focus on himself and be in a good place before starting a relationship. Having a girlfriend is not necessarily going to make him happy.
My personal experience - I had been dating a guy for many years - I know I wasn't happy with the relationship so being in a relationship did not make me happy. When I finally bit the bullet and broke up - I decided to just go out and have fun, do things I enjoyed. I did not want another relationship -- well in doing so I met so many great people and had many offers of dating -- I did ultimately meet the man I am now married to. I think being you and enjoying yourself opens you up so much more than desperately just searching for someone.
Also - if you feel he is really gloomy - more than just being a bit down on himself for not having a girlfriend - his college should have counseling services that just meeting and speaking a few times could help lift him. Especially if he feels really alone there.