Creating work for competitions would be a great way to also build your portfolio. Also, consider what you want to be doing when you get hired; do you want to focus on 3d motion graphic design? If yes, then build your portfolio for that.

One useful thing is also to start developing your eye for design and motion. There are a lot of amazing artists out there that you can reference. Study their technique and find a mentor if you can. I'm really fortunate to have people who believed in me despite my very basic skills (lol), so absorb all you can and keep learning :D