Honestly I like Peter's list a lot as a good general list and agree with his comment about the
XLR adapters.
Does your school have its own console/sound system? If so whats it comprised of? Are other people bringing in theirs?
If you have a lot of guest speakers and performers coming in what issues do you see repeatedly cropping up?
As for the kit on eBay...it feels like overkill to me. But I don't know it may not be in your situation.