| It depends entirely on musical style, your own sonic goals, cost vs personal value, and what you feel you are lacking in the me50b. There is no real way to say "Yes, go and buy a board and 9 effects right now" without knowing more.
That being said, good universal starting points are a tuner, a compressor, and some dirt (od, fuzz or distortion) or maybe start with getting individual pedals to replace the functions of the me50b that you feel are lacking. | 
