Some Candidates pack a box with things they feel they will need after Indoc before they leave home to be sent by their parents for when Indoc ends. Some of the items might include clear nail polish (for belt buckles), Febreeze, a bleach pen, study guide type books for calc & such, a bag of really sour or burning hot hard candy so you can try to keep yourself awake in classes, an electric razor....... There will be things that you'll find out about during Indoc that you might find you do or don't need so when you write home during that time, be sure to include those things so parents can take away or add to the box.
Going in, you might find it difficult to fit all the required items into one duffel. Try some of those travel bags that you pack then roll & squeeze the air out. Makes a huge difference. To the list they give you in the logging in instructions, add a small roll of duct tape & a small package of safety pins. Separate items into zip-loc baggies. Have an empty zip-loc at the ready to throw your watch, cell phone & charger into to put back into your duffel.
Keep in mind..... Your storage space will be small & with all that you're issued, you'll not have room for too many extra items. Everything has to be stowed & squared away. The more stuff you have, the more you'll have to mess with it. When it comes time to move to another room, you'll curse yourself for having "stuff" so be as frugal as you can.