Gaskets and clamps can both get reused. The trick is knowing what to look for. If the gasket isn't distorted or damaged or squashed it will reseal. I reuse them all the time. When they get crappy is when you see the graphite material starting to diminish and more mesh is showing.
Clamps are reusable too. As long as the hourglass shaped block isn't seized on the splines you're fine. If it seizes the nut will tighten but the clamp will still be loose. I just bought 2 today at $7 each. They do get worn and ratty.
“When the going gets weird, the weird turn professional....” ~ Hunter S. Thompson~
R.I.P. Rubberdown. 1971-2012