Talk:Shinkansen E5/@comment-24912217-20140801190754/@comment-5596770-20140802125518

If you are asking what the definition of a complete set is, a complete set is defined as using the locomotive from the train set and enough wagons from the train set to match the power of the locomotive. Not all wagon types are required.

In general, you will never be required to spend gems to buy wagons to complete contracts or achievements.