Of course, time of year is everything. But I'll assume you're thinking in terms of a summer trip, which means you can probably count on warm weather but need some backup in case the weather turns or the forecast's off.
My basic kit for such a trip goes like this, along with reasonably priced examples: Full set of long underwear: for summer use, I like Patagonia's Silkweight Capilene ($34 tops, $32 bottoms; www.patagonia.com);
Some sort of synthetic T-shirt: REI sells one made of CoolMax ($25; www.rei.com);
Good nylon hiking shorts: L.L. Bean Supplex Trail Cargo Shorts ($36; www.llbean.com);
A mid-weight fleece jacket: The North Face Salathe Jacket ($89; www.thenorthface.com);
Rainjacket and pants: Marmot Precip ($180 for a full set; www.marmot.com).
Sun hat, light gloves, warm hat, socks and boots are all sort of assumed, I think. I also like to pack a light fleece vest (Campmor Polartec 200 Fleece: $18; www.campmor.com).
Anyway, this setup will handle 90 percent of the weather you're apt to face, won't cost much, and won't weigh much. For each category, there are dozens of options, so don't feel tied to this. Well, except for the fact that I recommended it all, which sort of gold plates the whole deal...