beginner fish board ?

Hey im planning on buying my first surfboard and need some advice. I have had surf lessons in the past on big foam surfboards and can catch unbroken waves and surf down the face of the wave. I am looking to buy my first surfboard and need some advice on whether to buy a fish and what size i should go for. I am 15 years old 5,7ft and 57kg. I was wondering what size of fish i should go for and whether or not i should go for one at all. I dont want a huge longboard as i feel it would be difficult to move around with in and out of the water. i generally learn quickly when it comes to board sports and i want a board that will allow me to advance my surfing. Any advice would be much appreciated 
