There's an old saying that this makes me remember.
There are 3 very basic elements to tuning: speed, endurance, and price.
For the most part, those of us without a sweet hookup have to choose.
You can be fast and cheap, but it's not reliableYou can be reliable and cheap, but it's not fastYou can be fast and reliable, but it's not cheap
It's challenging to get things cheap and have them last a while, so I don't think I can reccommend any cheap place to you cause car parts are expensive and that's just that.
With this in mind, here are some places that at have a nice selection of parts.
http://www.tanabe-usa.com/http://www.splparts.com/And never forget ebay