I have free time after school priorities for "fun learning", yet I do not know what skills I'm expected to have to start building a portfolio for UI/UX practice. I'm not sure whether I should focus on learning graphic design, or web design, or front-end development, in addition to the philosophy I should learn - I am very confused.
If it is going to be "fun learning", then you should first think about what is interesting and fun for you to spend time on. Don't worry about the specifics because UX covers such a wide area and you can't do everything at once. I would consider UX a philosophy or approach rather than a specific technique or methodology, much in the same way that Agile doesn't prescribe a certain method (even though most people like the SCRUM method). You will definitely need to consider what your strength is (programming, design, research) and build your portfolio work around that first before branching out into other areas of UX design.
UX is not just UI. It is possible to do UX without going near interface design. If you want to focus on just the user interface then the title you should explore is Interaction Designer.
UX includes many areas like User Research, Content Strategy and Information Architecture that require different skill sets. The key thing that I and others want to see in a UX portfolio is process. I only have one final design in a 20 page portfolio as I rarely go near the implementation part. On the other hand if I was hiring a design or interaction designer...
When you start out the best way to get employed is to have good overall skills, including a grasp of visual design and front end tech. Then read up on user research and information architecture and keep on going from that point.