You're going to need some durable clothes for your hike. Clothes designed for athletics tend to be more pricey than normal clothes, but you'll be wearing the same stuff everyday. Consider good clothes to be an investment. Synthetic materials are the best because they're lightweight, and they dry quickly. Cotton is the worst. If it gets wet, it will be cold and take a long time to dry. Also, remember to layer your clothes if it's cold.
Keep in mind that the first month or two will be colder than the rest of your hike. It's likely that you'll run into snow in the Smokies. Some of your clothes can be mailed home or ditched in a hiker box once the weather warms up for good. These are just suggestions. You'll probably have your own preferences.
-synthetic t-shirt: this is pretty much a staple, and you'll probably wear it everyday.
-rain jacket: this is great to have because it not only keeps you dry, but you can wear it when you're cold too.
-convertible pants: they zip off above the knee, so they can be shorts or pants.
-long-sleeved shirt: good for nighttime or cold weather.
-synthetic shorts: something loose and breathable.
-wool socks: bring 2 or 3 pairs; you'll probably have to replace them a few times during your hike.
-sports bra (if necessary)
Other options:
-running skirt: these are getting pretty popular on the trail because they're super comfortable and they look cute.
-hiking kilt (for men): most guys think these are for wussies, until they give them a try and see how comfortable they are; I thought they were nerdy until I ran into one hiker that looked like a Gladiator in his kilt.
Cold weather clothes (send home when weather warms up):
-beanie/cap: keep your ears warm.
-gloves: you can probably get by without them if you don't want to carry them, but they're nice to have.
-yoga pants/ long underwear
-fleece/ flannel/ long-sleeve shirt
Of course you'll need a comfortable pair of hiking boots or shoes. A lot of hikers like to have a pair of sandals to wear around camp, as well.