I pretty much second what Mouse said: think layers.

I live and hike in Ohio and Kentucky, not a whole lot different from Tennessee. Just a couple of weekends ago, I was in the Mt. Rogers/Grayson Highlands area near Damascus, VA - right where Tennessee, North Carolina, West Virginia, and Kentucky touch Virginia. Nighttime temps were in the low 50's or upper 40's; morning and evening hiking in the high 50's, daytime hiking in the low 70's - with fog and light mist tossed in, just for grins and giggles. Sound familiar?

During the day, I wore shorts and a lightweight synthetic T-shirt (short sleeve); in my pack I had a down sweater-weight vest, a pair of midweight synthetic long-johns, and a midweight synthetic shirt. I also had windshirt and a lightweight synthetic beanie. I wore the windshirt most of the time, and addedd the other layers in the evening as needed. One morning, because it was chilly and misty, I wore my rain pants and rain jacket, and it was just right until the sun came out - then it was shorts, T-shirt, and windshirt again.

When I go out in cooler weather, I'll often hike in lightweight top and bottoms (worn under my shorts - I just don't like hiking in pants.) In my pack I'll have the midweight top and bottom, plus a down sweater (like the vest, but with arms.)

I've used MTS - it's pretty good stuff. I'd suggest a set of midweight top and bottom. (My lightweight set is mostly for hiking in cold weather.) Then add an insulating layer (a midweight fleece jacket is cheaper than down, and works just as well - it just takes up a little more pack space.) I think REI still has a house brand of fleece that is pretty good. A windbreaker (the lighter weight the better) is also a really versatile layer; if the budget won't quite stretch, let you rain jacket do double duty.

You might also check out Campmor's house brand of synthetic underwear and fleece - I used it when I had to outfit both me and my teenage son, and budget was more of an issue than now. It worked quite well, and was a really good value.

If you're out when it's a little colder than the long johns and fleece will handle, add your rain pants and jacket for a little more warmth - but in our neck of the woods, I've found it has to be down below freezing for that.