First off, thank you!
It's all about accessories. They are the spice of any outfit and you can find cute things everywhere.
For clothes, I absolutely adore ModCloth and Urban Outfitters, but I hardly ever buy anything unless it's on sale or relatively cheap. I frequent thrift shops, do DIY and whatnot. On the cheaper end of the spectrum, Target is a favorite, along with Forever 21, Wet Seal, and Fred Flare.
Just draw on what inspires you and go from there. Find someone whose style you admire and take elements from them and make it your own. Clothing is a form of expression, and a good outfit is a piece of art.