ok, depends if your an old codger who is scared of hights or not. if you are; the spleen door or some other hideously huge and limiting board will do for you

but if your like a normal person get something around 125-135 second hand or 130-135 new. make sure you get one that is light, has good reviews on some of the forums and has pads/straps that suit your feet.
definitely shop around as value for money is way better at some shops as to others [obviously not going to name names].
you dont need to buy a learners board, as unchained said; he was up and riding a 122 as his first board quick enough [3 hours on water max before going upwind on his good side] you can just hire the fat board in the mean time.
also you have a rather big kite...