The levels seem really easy so far, so a speed through seems really easy to me. I'd just try to get all the stars you can to try and really really enjoy the game.
speaking of stars, anyone know what level and world the 2nd Luigi star is? I got the photo but I can't remember what level/world it is. I think it's a world that I would get to using the Kitchen.
There are only 3 Luigi stars
First is in Good Egg
Second is in Battlerock, which is accessed from the fountain. This is also one of the three Green Power Stars.
Third will be in Honeyhive, accessed from the first dome.