Don't forget your kids... they might prove important at one point or another during the competition!
But in all seriousness, I would reccomend some kind of robot cart so you dont end up lifting it everywhere, some kind of mini-shopvac if you already have one, spare parts, enough tools for your own emergencies and your neighbor's occasional requests.
Everything is a compromise. My old team usually uses masking tape to draw out an 8x8ft square of floor to see how much space they really have in the pits. (8x8 is the minimum, but it is smart to plan for the worst and enjoy it if it turns out to be more). Doing this allows them to really say "We need this and have a space for it in the corner here" or "Not a single team in the regional is going to need that and they weigh a hundred pounds!"
Hope this helps!
Petrie