Double or triple butted spokes. If you want to save you can run double butted on the rear nds only, as they are the most likely to suffer fatigue failure. Probably doesn't matter which by very much. Stick with the larger brands—DT, Sapim, Wheelsmith, or Pillar. There's no real advantage to longer nipples, they usually have the same number of threads, and tension is only really held by a handful of threads anyways. High even tension and stress relieving will have the greatest impact on fatigue resistence.