Well....you are in the wrong hobby in you are looking for something cheap to do.
If you are looking to save some $$, try to hunt down a used CAI on the classified section or eBay, you may be able to find something. You could also buy a WAI and save some money. I bought my HKS intake for $180 and I really like it, sounds great and gives a nice jump in power. Or you could always stick w/ the homemade one. Your intake sounds interesting to say the least....there are a lot of people who have made their own, search the boards and I'm sure you can find a write up.
Other more cost effective upgrades would be to advance you timing (free if you have a timing light), make sure all your fluids are top of the line (this actually can make quite a difference), and check your plugs to make sure they are fine. Another cheap upgrade is some UR pullies (good for about 5 hp) and a short shifter. After that things tend to get expensive, if you have the money I would look at completing intake/header/exhaust as your first major project. Good luck.