Yosh!
First off, are you talking about Harajuku fashion? If so, I'd say that you should study the looks (Decora, Lolita, Visual Kei, etc.) until you get familiar with them. There are lots of online stores that you can buy these types of clothes from.
For the decora look, you can find lots of those things in the US. Claire's has the best decora jewelry. If you look in the kids section of many stores, they have good decora jewelry. As for the outfit, you can find track sweashirts and pastel-colored skirts anywhere.
For the Visual kei/punk look, I reccomend this site:
eBay Store - REFUSE TO BE USUAL: PUNK ROCK JROCK, GOTHIC LOLITA, JAPAN URBAN DIY and also the punk section of this one:
eBay Store - Little Chili Lolita Shop: Skirts, Shirt, NANA Rocking shoes strap. They both have reasonably-priced VK and Punk fashion.
For Lolita, I would reccomend both of those ebay sites (I got a Mar Jour sweet lolita dress from on of them, and the other has really cheap lolita shoes). Also, don't be afraid to buy American-made lolita, like this store:
Elegant Gothic Lolita Clothing and Accessories.
I hope this helps! I'm glad we have a new fan of Japanese fashion.