If it has to be only Fuji lenses, it becomes difficult.
16 27 90
16, because it's nice and wide enough and not too wide.
27, because you can do, er, everything with that lens.
90, because having used the 90mm for a wee bit I very much prefer it to the 56 (the latter being an awesome lens nonetheless).
My most used focal lengths are 25, 35, 50 and 70mm, but that doesn't match the op's question.