You have a couple of decent Guard Trainees especially Zailizam bin Mahadzir.
If you decide to train Guards I thing Jump Shot would be a good option in the beginning. Try to get some of the younger guys to reach Strong/Proficient in this and then sell them, and use the money to buy better trainees.
Jump Shot is by far the best guards skill if you want to sell. However, in order to get really good prices players should have a balanced skill set - and this is also important for contribution to your own team.
But keep Zailizam bin Mahadzir, he is a nice all round guard.