Depends on your personality. If you are like me, you will change your mind a dozen times before you are ready to move up.

Or you could just keep flying that trainer until you get rrreeeaaalll good at it (3D'ing), then your question will be more like "What do I want to fly next???"

btw-thats how I did it My 2nd plane is what most people would consider their 3rd plane