Top 1 priority is to make a balanced game. In its current state it's not, thanks to GS bug that is occuring since Season 28. So, GS is top priority.
Second priority is to fix the Game Engine: To ensure the minutes of trainees with no random changes in Garbage Time, to minimize unrealistic instances of players get fouled out in 10 minutes, things like that.
Third priority is to reshape the site, to be more accessible and pretty for the newcomers. Pretty site = succesfull company.
Last priority IMO is the app. It could be useful but not vital. I don't see myself needing the app... My smartphone handles the game quite well with some patience.