Don't know where to start on my game

I’ve been using UE4 for about a year now getting used to it and having fun creating random things, but now I want to actually create a project/game. The problem is I am completely lost when it comes to knowing what to do in order. I don’t know what to do from beginning to end. Should I code first, or make animations, or build a map first, etc. I need somewhat of an idea or agenda from start to finish.