It's kind of hard for me to tell for sure which needs improving, considering the time constraint aspect of the art jam.
I can give general advice, though.
The entire piece could definitely be smaller! It'd be a lot easier to animate, and you wouldn't be losing much because the piece hasn't got a lot of detail in the first place.
Things could be planned better with key frames. separate each action of the character (In this case it can be casting, walking up stairs, and entering portal), so the animating become easier and contained. Kinda like doing things in layers, but on a bigger scale. you can do a kind of transition animation between each part to make them all look smoother later on.