After we have finished #1 and #2, decide whether we want to:
Create more commands for the command line. This is the best option if we have very limited time and program memory space.
Create some "program" such as a simple game or some colour flashing (Disco Mode). This is probably the more ideal option as the result is more flashy and is perhaps not too complicated, depends if we have enough memory space in the Program Memory. (If there isn't enough space in PM then perhaps we can reduce the Data Memory a bit).
Create a simple Text Editor that is basically a glorified text buffer that also can read/write from a "file". The goal would be to also create a simple file system later which would also require the reading/writing to the static flash memory which might be hard, this makes this probably the least ideal option.
After we have finished #1 and #2, decide whether we want to: