Misty is a relatively easy character to recreate. You can do a number of things to make her as realistic as slutty or as accurate as you want. For her cosplay, I essentially used things I already owned. She's a great start for a beginner and is fairly iconic, so most people will know who you're trying to emulate!
Shirt - I bought her shirt from Forever 21. During the summer, they have a ton of bright neons that you can use for cosplay.
Shorts - An old pair of jean shorts I had. If you don't have a pair of jean shorts that roll up like that, you can easily make one by cutting up an old pair of jeans and rolling the fabric.
Suspenders - Hot topic. I think Claire's sells them too, but not in normal colors (mostly dumb things like skulls and flowers and Big Time Rush)
Shoes - Got them at sale at Sears. They're just red Keds and I used a shoe lace tutorial to figure out how to tie my laces so that they were straight like in the anime. Click here for the tutorial.