Go to the B/S/T forums and go look under "Miscellaneous Equipment." If you can find an Ion part out, that's your best bet, you can get some pretty good deals sometimes. And ya like they said above, don't rush the upgrading, just look for good deals and buy stuff then.
For a first upgrade get the Smart Parts 360 QEV, I would buy that new instead of used though. Only 20 bucks at any local paintball shop.