it really depends on what type of stuff you want to buy, if you want good quallity name brands, its going to be alot more then cheap ebay stuff. Some things you can get away with buying off ebay though. Ill give you a basic list of ebay priced parts, it might be more, it might be less, but its an idea.

intake, you can make your own fairly easy, but they are on ebay for like 30$,

headers, 40-60 on ebay, ive been told you get the same results with this as you do the name brand headers.
exhaust, a full catback on ebay will be about 200 shipped to the states, you can sometimes find deals with a header and catback for cheaper then buying them seperatly

spark wires/plugs just go to napa or autozone or something for these. shouldnt be over 60$ or so for good stuff.

a bigger tb, you can make these out of an old jeep tb and an eclipse tb, there is a write up on the wiki for it, or you can buy one. You could probably get the jeep one and spare eclipse one for under 40 depending on the junkyards.

a udp you can get on ebay for like 50$.

so you can get it all for like 450, but thats going the cheapest way possible, and it all goes back to the old saying that you can pick two things out of being fast, cheap, and reliable, but you cant have all three.