you should really focus on one part of the car at a time. Figure out how much you are willing to spend, and then start a list of parts that you would want to buy including the price. That's what I did.

basically, divide all your stuff into different categories:
Suspension/Chassis/Rims
Engine
Interior/Audio
Body/Lighting

it helped me clear my mind about my overall plans for my car. Now I wish I could actually follow through with it all