Always compare prices on commodity hardware between VEX, Robosource.net, Amazon, MSC, and your local hardware store.
Chances are you can get large packages of screws, zip-ties, and rubber bands at prices well below what Vex sells them for.
In addition to that, you will get wider selection and more colorful variety of parts to sprinkle some holiday spirit on your robot:
Also, you should check ebay and ask senior volunteers at your local event if any (graduating) team is willing to sell their surplus or older (steel) parts at discount.
Finally, don’t buy pneumatics. It has marginal educational value on top of basic kit imo. Instead, try to think creatively about using more cheaper VRC legal non-VEX parts, like rubber bands, zip-ties, rope, and spacers.