Hey there! I'm under the assumption that you'll be applying for an original character but feel free to correct me if I'm wrong since it will change the impact of my answer. Personally speaking, we would prefer there to be no gaps in regards to the history of the character as it may be vital to us when crafting motives and character-specific plot that might come up. If the "gaps" itself do not deal with your character or what happened to them, personally, then it shouldn't be a necessity, but if there are parts where it does, even in minor capacity, we would prefer that they be laid out.

If you wish to give me specifics, feel free to privately message me either via Dreamwidth or Plurk - whether it's on the mod account or on my main, as I can most likely give a more detailed answer.